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The Human Body—An Orientation
Anatomy
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Study of the structure and shape of the body and its parts
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Observation is used to see sizes and relationships of parts
Anatomy—Levels of Study
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Gross anatomy
o Large structures
o Easily observable
The Human Body—An Orientation
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Let’s look at an example of gross anatomy using the digestive system organs
Anatomy—Levels of Study
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Microscopic anatomy
o Structures cannot be seen with the naked eye
o Structures can be viewed only with a microscope
The Human Body—An Orientation
Physiology
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Study of how the body and its parts work or function
Relationship between Anatomy and Physiology
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Structure determines what functions can occur
If structure changes, the function must also change
Levels of Structural Organization
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Six levels of structural organization
1. Atoms
2. Cells
3. Tissues
4. Organs
5. Organ systems
6. Organisms
Organ System Overview
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Integumentary system
o Forms the external body covering (skin)
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o Protects deeper tissue from injury
o Helps regulate body temperature
o Location of cutaneous nerve receptors
Organ System Overview
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Skeletal system
o Consists of bones, cartilages, ligaments, and joints
o Supports the body
o Provides muscle attachment for movement
o Site of blood cell formation (hematopoiesis)
o Stores minerals
Organ System Overview
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Muscular system
o Skeletal muscles contract or shorten
o Produces movement of bones
Organ System Overview
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Nervous system
o Fast-acting control system
o Consists of brain, spinal cord, nerves, and sensory receptors
o Responds to internal and external change
o Sends messages via nerve impulses to central nervous system
o Central nervous system activates effectors (muscles and glands)
Organ System Overview
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Endocrine system
o Endocrine glands include:
 Pituitary gland
 Thyroid and parathyroids
 Adrenal glands
 Thymus
 Pancreas
 Pineal gland
 Ovaries (females) and testes (males)
Organ System Overview
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Endocrine system
o Secretes regulatory hormones
 Growth
 Reproduction
 Metabolism
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Organ System Overview
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Cardiovascular system
o Includes heart and blood vessels
 Heart pumps blood
 Vessels transport blood to tissues
o Transports materials in body via blood pumped by heart
 Oxygen and carbon dioxide
 Nutrients
 Wastes
Organ System Overview
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Lymphatic system
o Includes lymphatic vessels, lymph nodes, and lymphoid organs
o Returns leaked fluids back to blood vessels
o Cleanses the blood
o Involved in immunity
Organ System Overview
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Respiratory system
o Includes the nasal passages, pharynx, larynx, trachea, bronchi, and lungs
o Supplies blood with oxygen
o Removes carbon dioxide
Organ System Overview
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Digestive system
o Includes the oral cavity, esophagus, stomach, small and large intestines,
and accessory organs
o Breaks down food
o Allows for nutrient absorption into blood
o Eliminates indigestible material as feces
Organ System Overview
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Urinary system
o Includes the kidneys, ureters, urinary bladder, and urethra
o Eliminates nitrogenous wastes
o Maintains acid-base balance
o Regulates water and electrolytes
Organ System Overview
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Reproductive system
o For males, includes the testes, scrotum, penis, accessory glands, and duct
system
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 Testes produce sperm
 Duct system carries sperm to exterior
o For females, includes the ovaries, uterine tubes, uterus, and vagina
 Ovaries produce eggs
 Uterus provides site of development for fetus
Maintaining Life: Necessary Life Functions
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Maintain boundaries
Movement
o Locomotion
o Movement of substances
Responsiveness
o Ability to sense changes and react
Digestion
o Breakdown and absorption of nutrients
Necessary Life Functions
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Metabolism—chemical reactions within the body
o Break down complex molecules into smaller ones
o Build larger molecules from smaller ones
o Produces energy
o Regulated by hormones
Excretion
o Eliminates waste from metabolic reactions
o Wastes may be removed in urine or feces
Necessary Life Functions
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Reproduction
o Occurs on cellular level or organismal level
o Produces future generation
Growth
o Increases cell size and number of cells
Survival Needs
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Nutrients
o Chemicals for energy and cell building
o Includes carbohydrates, proteins, lipids, vitamins, and minerals
Oxygen
o Required for chemical reactions
Survival Needs
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Water
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o 60 to 80 percent of body weight
o Most abundant chemical in the human body
o Provides for metabolic reactions
Stable body temperature
o 37°C (98°F)
Atmospheric pressure
o Must be appropriate for gas exchange
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Homeostasis
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Homeostasis—maintenance of a stable internal environment
o A dynamic state of equilibrium
o Necessary for normal body functioning and to sustain life
Homeostatic imbalance
o A disturbance in homeostasis results in disease
Maintaining Homeostasis
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The body communicates through neural and hormonal control systems
o Receptor
 Responds to changes in the environment (stimuli)
 Sends information to control center along an afferent pathway
Maintaining Homeostasis
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Control center
o Determines set point
o Analyzes information
o Determines appropriate response
Effector
o Provides a means for response to the stimulus
o Information flows from control center to effector along efferent pathway
Feedback Mechanisms
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Negative feedback
o Includes most homeostatic control mechanisms
o Shuts off the original stimulus or reduces its intensity
o Works like a household thermostat
Feedback Mechanisms
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Positive feedback
o Increases the original stimulus to push the variable farther
o Reaction occurs at a faster rate
o In the body positive feedback occurs in blood clotting and during the birth of
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a baby
The Language of Anatomy
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Special terminology is used to prevent misunderstanding
Exact terms are used for:
o Position
o Direction
o Regions
o Structures
The Language of Anatomy
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Anatomical position
o Standard body position used to avoid confusion
o Terminology refers to this position regardless of actual body position
o Stand erect, feet parallel, arms hanging at the sides with palms facing
forward
Directional Terms
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Directional terms
o Explains location of one body structure in relation to another
Directional Terms
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Superior (cranial or cephalad): toward the head or upper part of a structure or the
body; above
Inferior (caudal): away from the head or toward the lower part of a structure or the
body; below
Directional Terms
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Ventral (anterior): toward or at the front of the body; in front of
Dorsal (posterior): toward or at the backside of the body; behind
Directional Terms
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Medial: toward or at the midline of the body; on the inner side of
Lateral: away from the midline of the body; on the outer side of
Intermediate: between a more medial and a more lateral structure
Directional Terms
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Proximal: close to the origin of the body part or point of attachment to a limb to the
body trunk
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Distal: farther from the origin of a body part or the point of attachment of a limb to the
body trunk
Directional Terms
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Superficial (external): toward or at the body surface
Deep (internal): away from the body surface; more internal
Regional Terms
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Anterior (ventral) body landmarks
Regional Terms
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Posterior (dorsal) body landmarks
Body Planes and Sections
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Sections are cuts along imaginary lines known as planes
Three types of planes or sections exist as right angles to one another
Body Planes and Sections
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A sagittal section divides the body (or organ) into left and right parts
A median, or midsagittal, section divides the body (or organ) into equal left and right
parts
A frontal, or coronal, section divides the body (or organ) into anterior and posterior
parts
A transverse, or cross, section divides the body (or organ) into superior and inferior
parts
Body Cavities
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Two body cavities
o Dorsal
o Ventral
Body cavities provide varying degrees of protection to organs within them
Body Cavities
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Dorsal body cavity has two subdivisions
1. Cranial cavity
 Houses the brain
 Protected by the skull
2. Spinal cavity
 Houses the spinal cord
 Protected by the vertebrae
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Body Cavities
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Ventral body cavity has two subdivisions separated by the diaphragm
1. Thoracic cavity
2. Abdominopelvic cavity
Body Cavities
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Thoracic cavity
o Cavity superior to the diaphragm
o Houses heart, lungs, and other organs
o Mediastinum, the central region, houses heart, trachea, and other organs
Body Cavities
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Abdominopelvic cavity
o Cavity inferior to the diaphragm
o Superior abdominal cavity contains the stomach, liver, and other organs
 Protected only by trunk muscles
o Inferior pelvic cavity contains reproductive organs, bladder, and rectum
 Protected somewhat by bony pelvis
o No physical structure separates abdominal from pelvic cavities
Body Cavities
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Abdominopelvic cavity subdivisions
o Four quadrants
o Nine regions
Body Cavities
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Other body cavities include:
o Oral and digestive cavities
o Nasal cavity
o Orbital cavities
o Middle ear cavities
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Matter and Energy
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Matter—anything that occupies space and has mass (weight)
Matter may exist as one of three states:
o Solid: definite shape and volume
o Liquid: definite volume; shape of container
o Gaseous: neither a definite shape nor volume
Matter and Energy
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Matter may be changed
o Physically
 Changes do not alter the basic nature of a substance
o Chemically
 Changes alter the chemical composition of a substance
Matter and Energy
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Energy—the ability to do work.
o Has no mass and does not take up space
o Kinetic energy: energy is doing work
o Potential energy: energy is inactive or stored
Matter and Energy
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Forms of energy
o Chemical energy is stored in chemical bonds of substances
o Electrical energy results from movement of charged particles
o Mechanical energy is energy directly involved in moving matter
o Radiant energy travels in waves
Matter and Energy
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Energy form conversions
o ATP (adenosine triphosphate) traps the chemical energy of food in its bonds
Composition of Matter
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Elements—fundamental units of matter
o 96 percent of the body is made from four elements:
1. Oxygen (O)
2. Carbon (C)
3. Hydrogen (H)
4. Nitrogen (N)
Periodic table contains a complete listing of elements
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Composition of Matter
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Atoms
o
o
o
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Building blocks of elements
Atoms of elements differ from one another
Atomic symbol is chemical shorthand for each element
Indivisible (“incapable of being divided”)
Subatomic Particles
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Nucleus
o Protons (p+) are positively charged
o Neutrons (n0) are uncharged or neutral
Orbiting the nucleus
o Electrons (e–) are negatively charged
Subatomic Particles
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Atoms are electrically neutral
o Number of protons equals numbers of electrons in an atom
o Positive and negative charges cancel each other out
Ions are atoms that have lost or gained electrons
Subatomic Particles
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Planetary model
o Portrays the atom as a miniature solar system
o Protons and neutrons are in the nucleus
o Electrons are in orbitals
Subatomic Particles
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Orbital model
o More modern
o Predicts chemical behavior of atoms
o Electrons are depicted by an electron cloud, a haze of negative charge,
outside the nucleus
Subatomic Particles
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Electrons determine an atom’s chemical behavior
Although outdated, the planetary model is simple and easy to understand and use
Identifying Elements
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Atomic number—equal to the number of protons that the atom contains
o Unique to atoms of a particular element
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o Indirectly tells the number of electrons in an atom
Atomic mass number—sum of the protons and neutrons contained in an atom’s
nucleus
Isotopes and Atomic Weight
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Isotopes
o Atoms of the same element with the same number of protons and the same
atomic number
o Vary in number of neutrons
Isotopes and Atomic Weight
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Atomic weight
o Close to mass number of most abundant isotope
o Atomic weight reflects natural isotope variation
Radioactivity
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Radioisotope
o Heavy isotope of certain atoms
o Tends to be unstable
o Decomposes to more stable isotope
Radioactivity—process of spontaneous atomic decay
Molecules and Compounds
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Molecule—two or more atoms of the same elements combined chemically
Example of a chemical reaction resulting in a molecule:
H (atom) + H (atom) → H2 (molecule)
o The reactants are the atoms on the left
o The product is the molecule on the right represented by a molecular formula
Molecules and Compounds
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Compound—two or more atoms of different elements combined chemically to form a
molecule of a compound
Example of a chemical reaction resulting in a compound:
4H + C → CH4 (methane)
Chemical Reactions
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Chemical reactions occur when atoms combine with or dissociate from other atoms
o Atoms are united by chemical bonds
o Atoms dissociate from other atoms when chemical bonds are broken
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Electrons and Bonding
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Electrons occupy energy levels called electron shells (levels)
Electrons closest to the nucleus are most strongly attracted
Each shell has distinct properties
o The number of electrons has an upper limit
o Shells closest to the nucleus fill first
Electrons and Bonding
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Bonding involves only interactions between electrons in the outer (valence) shell
Atoms with full valence shells do not form bonds
Inert Elements
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Atoms are stable (inert) when the outermost (valence) shell is complete
How to fill the atom’s shells
o Shell 1 can hold a maximum of 2 electrons
o Shell 2 can hold a maximum of 8 electrons
o Shell 3 can hold a maximum of 18 electrons
Inert Elements
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Rule of eights
o Atoms are considered stable when their outermost orbital has 8 electrons
o The exception to this rule of eights is shell 1, which can hold only 2 electrons
Reactive Elements
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Outermost valence shell is incomplete
Atoms will gain, lose, or share electrons to complete their outermost orbitals
o Atoms reach a stable state
o Bond formation produces a stable valence shell
Chemical Bonds
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Ionic bonds
o Form when electrons are completely transferred from one atom to another
o Allow atoms to achieve stability through the transfer of electrons
Chemical Bonds
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Ions
o Result from the loss or gain of electrons
 Anions have negative charge due to gain of electron(s)
 Cations have positive charge due to loss of electron(s)
o Tend to stay close together because opposite charges attract
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Chemical Bonds
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Covalent bonds
o Atoms become stable through shared electrons
o Electrons are shared in pairs
o Single covalent bonds share one pair of electrons
o Double covalent bonds share two pairs of electrons
Covalent Bonds
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Covalent bonds are either nonpolar or polar
o Nonpolar
 Electrons are shared equally between the atoms of the molecule
 Electrically neutral as a molecule
 Example: carbon dioxide
Covalent Bonds
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Covalent bonds are either nonpolar or polar
o Polar
 Electrons are not shared equally between the atoms of the molecule
 Molecule has a positive and negative side, or pole
 Example: water
Hydrogen Bonds
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Hydrogen bonds
o Weak chemical bonds
o Hydrogen is attracted to the negative portion of a polar molecule
o Provides attraction between molecules
o Responsible for the surface tension of water
o Important for forming intramolecular bonds, as in protein structure
Patterns of Chemical Reactions
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Synthesis reaction (A + B → AB)
o Atoms or molecules combine
o Energy is absorbed for bond formation
o Underlies all anabolic activities in the body
Decomposition reaction (AB → A + B)
o Molecule is broken down
o Chemical energy is released
o Underlies all catabolic activities in the body
Patterns of Chemical Reactions
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Exchange reaction (AB + C → AC + B and AB + CD → AD + CB)
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o Involves both synthesis and decomposition reactions as bonds are both
made and broken
o Switch is made between molecule parts, and different molecules are made
Patterns of Chemical Reactions
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Most chemical reactions are reversible
Reversibility is indicated by a double arrow
o When arrows differ in length, the longer arrow indicates the more rapid
reaction or major direction of progress
Factors influencing the rate of chemical reactions are shown in Table 2.4
Biochemistry: Essentials for Life
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Inorganic compounds
Lack carbon
Tend to be small, simple molecules
Include water, salts, and some acids and bases
Organic compounds
Contain carbon
All are large, covalently bonded molecules
Include carbohydrates, lipids, proteins, and nucleic acids
Important Inorganic Compounds
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Water
o Most abundant inorganic compound in the body
o Vital properties
 High heat capacity
 Polarity/solvent properties
 Chemical reactivity
 Cushioning
Important Inorganic Compounds
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High heat capacity: water absorbs and releases a large amount of heat before it
changes temperature
o Prevents sudden changes in body temperature
Important Inorganic Compounds
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Polarity/solvent properties: water is often called the “universal solvent”
o Solvents are liquids or gases that dissolve smaller amounts of solutes
o Solutes are solids, liquids, or gases that are dissolved or suspended by
solvents
o Solution forms when solutes are very tiny
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o Colloid forms when solutes of intermediate size form a translucent mixture
Important Inorganic Compounds
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Chemical reactivity
o Water is an important reactant in some chemical reactions
o Reactions that require water are known as hydrolysis reactions
o Example: water helps digest food or break down biological molecules
Important Inorganic Compounds
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Cushioning
o Water serves a protective function
o Examples: cerebrospinal fluid protects the brain from physical trauma, and
amniotic fluid protects a developing fetus
Important Inorganic Compounds
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Salts
o Contain cations other than H+ and anions other than OH–
o Easily dissociate (break apart) into ions in the presence of water
o Vital to many body functions
 Example: sodium and potassium ions are essential for nerve
impulses
Important Inorganic Compounds
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Salts
o All salts are electrolytes
o Electrolytes are ions that conduct electrical currents
Important Inorganic Compounds
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Acids
o
o
o
o
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Release hydrogen ions (H+) when dissolved in water
Are proton donors, since hydrogen ions are essentially a hydrogen nucleus
Example: HCl → H+ + Cl–
Strong acids ionize completely and liberate all their protons
Weak acids ionize incompletely
Important Inorganic Compounds
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Bases
o Release hydroxyl ions (OH–) when dissolved in water
o Are proton acceptors
o Example: NaOH → Na+ + OH–
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o Strong bases seek hydrogen ions
Important Inorganic Compounds
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Neutralization reaction
o Type of exchange reaction in which acids and bases react to form water and
a salt
o Example: NaOH + HCl → H2O + NaCl
pH
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Measures relative concentration of hydrogen ions
Based on the number of protons in a solution, expressed in terms of moles per liter
Each successive change on the pH scale represents a tenfold change in H+
concentration
pH
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pH 7 = neutral
o Number of hydrogen ions exactly equals the number of hydroxyl ions
pH below 7 = acidic
pH above 7 = basic
Buffers—chemicals that can regulate pH change
Chemical Reactions
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Polymer: chainlike molecules made of many similar or repeating units (monomers)
Many biological molecules are polymers, such as carbohydrates and proteins
Chemical Reactions
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Dehydration synthesis—monomers are joined to form polymers through the removal
of water molecules
o A hydrogen ion is removed from one monomer while a hydroxyl group is
removed from the monomer it is to be joined with
o Monomers unite, and water is released
Chemical Reactions
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Hydrolysis—polymers are broken down into monomers through the addition of water
molecules
o As a water molecule is added to each bond, the bond is broken, and the
monomers are released
Important Organic Compounds
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Carbohydrates
o Contain carbon, hydrogen, and oxygen
o Include sugars and starches
o Classified according to size
 Monosaccharides—simple sugars
 Disaccharides—two simple sugars joined by dehydration synthesis
 Polysaccharides—long-branching chains of linked simple sugars
Carbohydrates
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Monosaccharides—simple sugars
o Single chain or single-ring structures
o Contain 3 to 7 carbon atoms
o Examples: glucose (blood sugar), fructose, galactose, ribose, deoxyribose
Carbohydrates
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Disaccharides—two simple sugars joined by dehydration synthesis
o Examples include sucrose, lactose, and maltose
Carbohydrates
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Polysaccharides: long, branching chains of linked simple sugars
o Large, insoluble molecules
o Function as storage products
o Examples include starch and glycogen
Important Organic Compounds
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Lipids
o Most abundant are the triglycerides, phospholipids, and steroids
o Contain carbon, hydrogen, and oxygen
 Carbon and hydrogen outnumber oxygen
o Insoluble in water, but soluble in other lipids
Lipids
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Common lipids in the human body
o Neutral fats (triglycerides)
 Found in fat deposits
 Source of stored energy
 Composed of three fatty acids and one glycerol molecule
• Saturated fatty acids
• Unsaturated fatty acids
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Lipids
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Saturated fats
o Contain only single covalent bonds
o Chains are straight
o Exist as solids at room temperature since molecules pack closely together
Unsaturated fats
o Contain one or more double covalent bonds causing chains to kink
o Exist as liquid oils at room temperature
o Heart healthy
Lipids
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Trans fats
o Oils that have been solidified by the addition of hydrogen atoms at double
bond sites
o Increase risk of heart disease
Omega-3 fatty acids
o Found in cold-water fish and plant sources, including flax, pumpkin, and
chia seeds; walnuts and soy foods
o Appears to decrease risk of heart disease
Lipids
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Common lipids in the human body (continued)
o Phospholipids
 Contain two fatty acids rather than three
 Phosphorus-containing “head” carries an electrical charge and is
polar
 Charged region interacts with water and ions while the fatty acid
chains (“tails”) do not
 Form cell membranes
Lipids
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Common lipids in the human body (continued)
o Steroids
o Formed of four interlocking rings
o Include cholesterol, bile salts, vitamin D, and some hormones
o Some cholesterol is ingested from animal products. The liver also makes
cholesterol
o Cholesterol is the basis for all steroids made in the body
Important Organic Compounds
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Proteins
o Account for over half of the body’s organic matter
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 Provide for construction materials for body tissues
 Play a vital role in cell function
 Act as enzymes, hormones, and antibodies
o Contain carbon, oxygen, hydrogen, nitrogen, and sometimes sulfur
o Built from amino acids
Proteins
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Amino acid structure
o Contain an amine group (NH2)
o Contain an acid group (COOH)
o Vary only by R groups
Proteins
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Protein structure
o Polypeptides contain fewer than 50 amino acids
o Large proteins may have 50 to thousands of amino acids
o Sequence of amino acids produces a variety of proteins
Proteins
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Structural levels of proteins
o Primary structure
o Secondary structure
 Alpha helix
 Beta-pleated sheet
o Tertiary structure
o Quaternary structure
Proteins
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Fibrous (structural) proteins
o Appear in body structures
o Exhibit secondary, tertiary, or even quaternary structure
o Bind structures together and exist in body tissues
o Stable proteins
o Examples include collagen and keratin
Proteins
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Globular (functional) proteins
o Function as antibodies, hormones, or enzymes
o Exhibit at least tertiary structure
o Can be denatured and no longer perform physiological roles
o Active sites “fit” and interact chemically with other molecules
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Enzymes
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Act as biological catalysts
Increase the rate of chemical reactions
Bind to substrates at an active site to catalyze reactions
Recognize enzymes by their –ase suffix
o Hydrolase
o Oxidase
Important Organic Compounds
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Nucleic acids
o Make up genes
o Composed of carbon, oxygen, hydrogen, nitrogen, and phosphorus atoms
o Largest biological molecules in the body
Nucleic Acids
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Built from nucleotides containing three parts:
1. A nitrogenous base
 A = Adenine
 G = Guanine
 C = Cytosine
 T = Thymine
 U = Uracil
2. Pentose (five-carbon) sugar
3. A phosphate group
Nucleic Acids
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Deoxyribonucleic acid (DNA)
o The genetic material found within the cell’s nucleus
o Provides instructions for every protein in the body
o Organized by complimentary bases to form a double-stranded helix
o Contains the sugar deoxyribose and the bases adenine, thymine, cytosine,
and guanine
o Replicates before cell division
Nucleic Acids
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Ribonucleic acid (RNA)
o Carries out DNA’s instructions for protein synthesis
o Created from a template of DNA
o Organized by complementary bases to form a single-stranded helix
o Contains the sugar ribose and the bases adenine, uracil, cytosine, and
guanine
o Three varieties are messenger, transfer, and ribosomal RNA
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Nucleic Acids
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Adenosine triphosphate (ATP)
o Composed of a nucleotide built from ribose sugar, adenine base, and three
phosphate groups
o Chemical energy used by all cells
o Energy is released by breaking high-energy phosphate bond
o ATP is replenished by oxidation of food fuels
Nucleic Acids
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ADP (adenosine diphosphate) accumulates as ATP is used for energy
Three examples of how ATP drives cellular work are shown next
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Cells
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Cells are the structural units of all living things
The human body has 50 to 100 trillion cells
Four Concepts of the Cell Theory
1. A cell is the basic structural and functional unit of living organisms.
2. The activity of an organism depends on the collective activities of its cells.
3. According to the principle of complementarity, the biochemical activities of cells
are dictated by the relative number of their specific subcellular structures.
4. Continuity of life has a cellular basis.
Chemical Components of Cells
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Most cells are composed of four elements:
1. Carbon
2. Hydrogen
3. Oxygen
4. Nitrogen
Cells are about 60% water
Anatomy of a Generalized Cell
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In general, a cell has three main regions or parts:
1. Nucleus
2. Cytoplasm
3. Plasma membrane
The Nucleus
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Control center of the cell
o Contains genetic material known as deoxyribonucleic acid, or DNA
 DNA is needed for building proteins
 DNA is necessary for cell reproduction
Three regions:
1. Nuclear envelope (membrane)
2. Nucleolus
3. Chromatin
The Nucleus
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Nuclear envelope (membrane)
o Consists of a double membrane that bounds the nucleus
o Contains nuclear pores that allow for exchange of material with the rest of
the cell
o Encloses the jellylike fluid called the nucleoplasm
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The Nucleus

Nucleoli
o Nucleus contains one or more nucleoli
o Sites of ribosome assembly
o Ribosomes migrate into the cytoplasm through nuclear pores to serve as
the site of protein synthesis
The Nucleus

Chromatin
o Composed of DNA and protein
o Present when the cell is not dividing
o Scattered throughout the nucleus
o Condenses to form dense, rod-like bodies called chromosomes when the
cell divides
Plasma Membrane



Transparent barrier for cell contents
Contains cell contents
Separates cell contents from surrounding environment
Plasma Membrane

Fluid mosaic model is constructed of:
o Phospholipids
o Cholesterol
o Proteins
o Sugars
Plasma Membrane

Fluid mosaic model
o Phospholipid arrangement
 Hydrophilic (“water-loving”) polar “heads” are oriented on the inner
and outer surfaces of the membrane
 Hydrophobic (“water-hating”) nonpolar “tails” form the center
(interior) of the membrane
Plasma Membrane

Fluid mosaic model
o Phospholipid arrangement
 The hydrophobic interior makes the plasma membrane
impermeable to most water-soluble molecules
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Plasma Membrane

Fluid mosaic model
o Proteins
 Responsible for specialized functions
 Roles of proteins
• Enzymes
• Receptors
• Transport as channels or carriers
Plasma Membrane

Fluid mosaic model
o Sugars
 Glycoproteins are branched sugars attached to proteins that abut
the extracellular space
 Glycocalyx is the fuzzy, sticky, sugar-rich area on the cell’s surface
Plasma Membrane Junctions
 Membrane junctions
o Cells are bound together in three ways:
1. Glycoproteins in the glycocalyx act as an adhesive or cellular glue
2. Wavy contours of the membranes of adjacent cells fit together in a
tongue-and-groove fashion
3. Special membrane junctions are formed, which vary structurally
depending on their roles
Plasma Membrane Junctions

Membrane junctions
o Tight junctions
 Impermeable junctions
 Bind cells together into leakproof sheets
 Prevent substances from passing through extracellular space
between cells
Plasma Membrane Junctions

Membrane junctions
o Desmosomes
 Anchoring junctions that prevent cells from being pulled as a result
of mechanical stress
 Created by buttonlike thickenings of adjacent plasma membranes
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Plasma Membrane Junctions

Membrane junctions
o Gap junctions
 Allow communication between cells
 Hollow cylinders of proteins (connexons) span the width of the
abutting membranes
 Molecules can travel directly from one cell to the next through these
channels
Cytoplasm
o The material outside the nucleus and inside the plasma membrane
o Site of most cellular activities
Cytoplasm

Contains three major elements
o Cytosol
 Fluid that suspends other elements
o Organelles
 Metabolic machinery of the cell
 “Little organs” that perform functions for the cell
o Inclusions
 Chemical substances, such as stored nutrients or cell products
Cytoplasmic Organelles

Organelles
o Specialized cellular compartments
o Many are membrane-bound
o Compartmentalization is critical for organelle’s ability to perform
specialized functions
Cytoplasmic Organelles

Mitochondria
o “Powerhouses” of the cell
o Change shape continuously
o Mitochondrial wall consists of a double membrane with cristae on the inner
membrane
o Carry out reactions where oxygen is used to break down food
o Provides ATP for cellular energy
Cytoplasmic Organelles

Ribosomes
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o
o
o
o
Bilobed dark bodies
Made of protein and ribosomal RNA
Sites of protein synthesis
Found at two locations:
 Free in the cytoplasm
 As part of the rough endoplasmic reticulum
Cytoplasmic Organelles

Endoplasmic reticulum (ER)
o Fluid-filled cisterns (tubules or canals) for carrying substances within the
cell
o Two types:
 Rough ER
 Smooth ER
Cytoplasmic Organelles

Endoplasmic reticulum (ER)
o Rough endoplasmic reticulum
 Studded with ribosomes
 Synthesizes proteins
 Transport vesicles move proteins within cell
 Abundant in cells that make and export proteins
Cytoplasmic Organelles

Endoplasmic reticulum (ER)
o Smooth endoplasmic reticulum
 Functions in lipid metabolism
 Detoxification of drugs and pesticides
Cytoplasmic Organelles

Golgi apparatus
o Appears as a stack of flattened membranes associated with tiny vesicles
o Modifies and packages proteins arriving from the rough ER via transport
vesicles
o Produces different types of packages
 Secretory vesicles (pathway 1)
 In-house proteins and lipids (pathway 2)
 Lysosomes (pathway 3)
Cytoplasmic Organelles

Lysosomes
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o
o
o
o
Membranous “bags” packaged by the Golgi apparatus
Contain enzymes produced by ribosomes
Enzymes can digest worn-out or nonusable cell structures
House phagocytes that dispose of bacteria and cell debris
Cytoplasmic Organelles

Peroxisomes
o Membranous sacs of oxidase enzymes
 Detoxify harmful substances such as alcohol and formaldehyde
 Break down free radicals (highly reactive chemicals)
 Free radicals are converted to hydrogen peroxide and then to water
o Replicate by pinching in half or budding from the ER
Cytoplasmic Organelles

Cytoskeleton
o Network of protein structures that extend throughout the cytoplasm
o Provides the cell with an internal framework
o Three different types of elements:
1. Microfilaments (largest)
2. Intermediate filaments
3. Microtubules (smallest)
Cytoplasmic Organelles

Centrioles
o Rod-shaped bodies made of microtubules
o Generate microtubules
o Direct the formation of mitotic spindle during cell division
Cell Extension

Surface extensions found in some cells
o Cilia move materials across the cell surface
 Located in the respiratory system to move mucus
o Flagella propel the cell
 The only flagellated cell in the human body is sperm
o Microvilli are tiny, fingerlike extensions of the plasma membrane
 Increase surface area for absorption
Cell Diversity



The human body houses over 200 different cell types
Cells vary in length from 1/12,000 of an inch to over 1 yard (nerve cells)
Cell shape reflects its specialized function
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Cell Diversity

Cells that connect body parts
o Fibroblast
 Secretes cable-like fibers
o Erythrocyte (red blood cell)
 Carries oxygen in the bloodstream
Cell Diversity

Cells that cover and line body organs
o Epithelial cell
 Packs together in sheets
 Intermediate fibers resist tearing during rubbing or pulling
Cell Diversity

Cells that move organs and body parts
o Skeletal muscle and smooth muscle cells
 Contractile filaments allow cells to shorten forcefully
Cell Diversity

Cell that stores nutrients
o Fat cells
 Lipid droplets stored in cytoplasm
Cell Diversity

Cell that fights disease
o Macrophage (a phagocytic cell)
 Digests infectious microorganisms
Cell Diversity

Cell that gathers information and controls body functions
o Nerve cell (neuron)
 Receives and transmits messages to other body structures
Cell Diversity

Cells of reproduction
o Oocyte (female)
 Largest cell in the body
 Divides to become an embryo upon fertilization
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o Sperm (male)
 Built for swimming to the egg for fertilization
 Flagellum acts as a motile whip
Cell Physiology

Cells have the ability to:
o Metabolize
o Digest food
o Dispose of wastes
o Reproduce
o Grow
o Move
o Respond to a stimulus
Membrane Transport

Solution—homogeneous mixture of two or more components
o Solvent—dissolving medium; typically water in the body
o Solutes—components in smaller quantities within a solution
Membrane Transport


Intracellular fluid
o Nucleoplasm and cytosol
o Solution containing gases, nutrients, and salts dissolved in water
Interstitial fluid
o Fluid on the exterior of the cell
o Contains thousands of ingredients, such as nutrients, hormones,
neurotransmitters, salts, waste products
Membrane Transport

The plasma membrane is a selectively permeable barrier
o Some materials can pass through while others are excluded
o For example:
 Nutrients can enter the cell
 Undesirable substances are kept out
Membrane Transport

Two basic methods of transport
o Passive processes
 No energy (ATP) is required
o Active processes
 Cell must provide metabolic energy (ATP)
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Passive Processes

Diffusion
o Particles tend to distribute themselves evenly within a solution
o Driving force is the kinetic energy (energy of motion) that causes the
molecules to move about randomly
Passive Processes

Diffusion
o Molecule movement is from high concentration to low concentration, or
down a concentration gradient
o Size of molecule and temperature affects the speed of diffusion
 The smaller the molecule, the faster the rate of diffusion
 The warmer the molecule, the faster the rate of diffusion
Passive Processes

Example of diffusion:
o Pour a cup of coffee and drop in a cube of sugar
o Do not stir the sugar into the coffee; leave the cup of coffee sitting all day,
and it will taste sweet at the end of the day.
o Molecules move by diffusion and sweeten the entire cup
Passive Processes

Molecules will move by diffusion if any of the following applies:
o The molecules are small enough to pass through the membrane’s pores
(channels formed by membrane proteins)
o The molecules are lipid-soluble
o The molecules are assisted by a membrane carrier
Passive Processes

Types of diffusion
o Simple diffusion
 An unassisted process
 Solutes are lipid-soluble or small enough to pass through
membrane pores
Passive Processes

Types of diffusion (continued)
o Osmosis—simple diffusion of water
 ighly polar water molecules easily cross the plasma membrane
through aquaporins
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
Water moves down its concentration gradient
Passive Processes

Osmosis—A Closer Look
o Isotonic solutions have the same solute and water concentrations as cells
and cause no visible changes in the cell
o Hypertonic solutions contain more solutes than the cells do; the cells will
begin to shrink
o Hypotonic solutions contain fewer solutes (more water) than the cells do;
cells will plump
Passive Processes

Types of diffusion (continued)
o Facilitated diffusion
 Transports lipid-insoluble and large substances
 Glucose is transported via facilitated diffusion
 Protein membrane channels or protein molecules that act as
carriers are used
Passive Processes

Filtration
o Water and solutes are forced through a membrane by fluid, or hydrostatic
pressure
o A pressure gradient must exist
 Solute-containing fluid (filtrate) is pushed from a high-pressure area
to a lower-pressure area
 Filtration is critical for the kidneys to work properly
Active Processes



Sometimes called solute pumping
Requires protein carriers to transport substances that:
o May be too large to travel through membrane channels
o May not be lipid-soluble
o May have to move against a concentration gradient
ATP is used for transport
Active Processes

Active transport
o Amino acids, some sugars, and ions are transported by protein carriers
known as solute pumps
o ATP energizes solute pumps
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o In most cases, substances are moved against concentration (or electrical)
gradients
Active Processes

Example of active transport is the sodium-potassium pump
o Sodium is transported out of the cell
o Potassium is transported into the cell
Active Processes

Vesicular transport: substances are moved without actually crossing the plasma
membrane
o Exocytosis
o Endocytosis
 Phagocytosis
 Pinocytosis
Active Processes


Vesicular transport (continued)
o Exocytosis
Moves materials out of the cell
o Material is carried in a membranous sac called a vesicle
o Vesicle migrates to plasma membrane
o Vesicle combines with plasma membrane
o Material is emptied to the outside
o Refer to Pathway 1 in Figure 3.6
Active Processes

Vesicular transport (continued)
o Exocytosis docking process
 Transmembrane proteins on the vesicles are called
v-SNAREs (v for vesicle)
 Plasma membrane proteins are called t-SNAREs
(t for target)
 v-SNAREs recognize and bind t-SNAREs
 Membranes corkscrew and fuse together
Active Processes

Vesicular transport (continued)
o Endocytosis
 Extracellular substances are engulfed by being enclosed in a
membranous vescicle
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


Vesicle typically fuses with a lysosome
Contents are digested by lysosomal enzymes
In some cases, the vesicle is released by exocytosis on the
opposite side of the cell
Active Processes

Vesicular transport (continued)
o Types of endocytosis
 Phagocytosis—“cell eating”
• Cell engulfs large particles such as bacteria or dead body
cells
• Pseudopods are cytoplasmic extensions that separate
substances (such as bacteria or dead body cells) from
external environment
• Phagocytosis is a protective mechanism, not a means of
getting nutrients
Active Processes

Vesicular transport (continued)
o Types of endocytosis
2. Pinocytosis—“cell drinking”
• Cell “gulps” droplets of extracellular fluid containing
dissolved proteins or fats
• Plasma membrane forms a pit, and edges fuse around
droplet of fluid
• Routine activity for most cells, such as those involved in
absorption (small intestine)
Active Processes

Vesicular transport (continued)
o Types of endocytosis
3. Receptor-mediated endocytosis
• Method for taking up specific target molecules
• Receptor proteins on the membrane surface bind only
certain substances
• Highly selective process of taking in substances such as
enzymes, some hormones, cholesterol, and iron
Active Processes

Vesicular transport (continued)
o Types of endocytosis
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3. Receptor-mediated endocytosis
• Both the receptors and target molecules are in a vesicle
• Contents of the vesicles are dealt with in one of the ways
shown in the next figure
Cell Life Cycle

Cell life cycle is a series of changes the cell experiences from the time it is
formed until it divides
Cell Life Cycle

Cycle has two major periods
o Interphase
 Cell grows
 Cell carries on metabolic processes
 Longer phase of the cell cycle
o Cell division
 Cell replicates itself
 Function is to produce more cells for growth and repair processes
DNA Replication


Genetic material is duplicated and readies a cell for division into two cells
Occurs toward the end of interphase
DNA Replication



DNA uncoils into two nucleotide chains, and each side serves as a template
Nucleotides are complementary
o Adenine (A) always bonds with thymine (T)
o Guanine (G) always bonds with cytosine (C)
For example, TACTGC bonds with new nucleotides in the order ATGACG
Events of Cell Division


Mitosis—division of the nucleus
o Results in the formation of two daughter nuclei
Cytokinesis—division of the cytoplasm
o Begins when mitosis is near completion
o Results in the formation of two daughter cells
Stages of Mitosis

Prophase
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o First part of cell division
o Chromatin coils into chromosomes
 Chromosomes are held together by a centromere
 A chromosome has two strands
 Each strand is called a chromatid
Stages of Mitosis

Prophase (continued)
o Centrioles migrate to the poles to direct assembly of mitotic spindle fibers
 Mitotic spindles are made of microtubules
 Spindle provides scaffolding for the attachment and movement of
the chromosomes during the later mitotic stages
o Nuclear envelope breaks down and disappears
Stages of Mitosis

Metaphase
o Chromosomes are aligned in the center of the cell on the metaphase plate
 Metaphase plate is the center of the spindle midway between the
centrioles
o Straight line of chromosomes is now seen
Stages of Mitosis

Anaphase
o Centromere splits
o Chromatids move slowly apart and toward the opposite ends of the cell
o Anaphase is over when the chromosomes stop moving
Stages of Mitosis

Telophase
o Reverse of prophase
o Chromosomes uncoil to become chromatin
o Spindles break down and disappear
o Nuclear envelope reforms around chromatin
o Nucleoli appear in each of the daughter nuclei
Stages of Mitosis

Cytokinesis
o Division of the cytoplasm
o Begins during late anaphase and completes during telophase
o A cleavage furrow forms to pinch the cells into two parts
 Cleavage furrow is a contractile ring made of microfilaments
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Stages of Mitosis




Two daughter cells exist at the end of cell division
In most cases, mitosis and cytokinesis occur together
In some cases, the cytoplasm is not divided
o Binucleate or multinucleate cells result
o Common in the liver
Mitosis gone wild is the basis for tumors and cancers
Protein Synthesis



DNA serves as a blueprint for making proteins
Gene: DNA segment that carries a blueprint for building one protein or
polypeptide chain
Proteins have many functions
o Fibrous (structural) proteins are the building materials for cells
o Globular (functional) proteins act as enzymes (biological catalysts)
Protein Synthesis



DNA information is coded into triplets
Triplets
o Contain three bases
o Call for a particular amino acid
For example, a DNA sequence of AAA specifies the amino acid phenylalanine
Protein Synthesis



Most ribosomes, the manufacturing sites of proteins, are located in the cytoplasm
DNA never leaves the nucleus in interphase cells
DNA requires a decoder and a messenger to build proteins, both are functions
carried out by RNA (ribonucleic acid)
Protein Synthesis

How does RNA differ from DNA? RNA:
o Is single-stranded
o Contains ribose sugar instead of deoxyribose
o Contains uracil (U) base instead of thymine (T)
Role of RNA

Transfer RNA (tRNA)
o Transfers appropriate amino acids to the ribosome for building the protein
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

Ribosomal RNA (rRNA)
o Helps form the ribosomes where proteins are built
Messenger RNA (mRNA)
o Carries the instructions for building a protein from the nucleus to the
ribosome
Role of RNA


Protein synthesis involves two major phases:
o Transcription
o Translation
We will detail these two phases next
Protein Synthesis

Transcription
o Transfer of information from DNA’s base sequence to the complementary
base sequence of mRNA
o Only DNA and mRNA are involved
o Triplets are the three-base sequence specifying a particular amino acid on
the DNA gene
o Codons are the corresponding three-base sequences on mRNA
Protein Synthesis

Example of transcription:
o DNA triplets
AAT-CGT-TCG
o mRNA codons
UUA-GCA-AGC
Protein Synthesis

Translation
o Base sequence of nucleic acid is translated to an amino acid sequence
o Amino acids are the building blocks of proteins
Protein Synthesis

Translation (continued)
o Steps correspond to Figure 3.16 (step 1 covers transcription)
2. mRNA leaves nucleus and attaches to ribosome, and translation
begins
3. Incoming tRNA recognizes a complementary mRNA codon calling
for its amino acid by binding via its anticodon to the codon.
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Protein Synthesis

Translation (continued)
o Steps correspond to Figure 3.16
4. As the ribosome moves along the mRNA, a new amino acid is
added to the growing protein chain.
5. Released tRNA reenters the cytoplasmic pool, ready to be
recharged with a new amino acid.
Body Tissues

Tissues
o Groups of cells with similar structure and function
o Four primary types:
1. Epithelial tissue (epithelium)
2. Connective tissue
3. Muscle tissue
4. Nervous tissue
Epithelial Tissues


Locations:
o Body coverings
o Body linings
o Glandular tissue
Functions:
o Protection
o Absorption
o Filtration
o Secretion
Epithelium Characteristics





Cells fit closely together and often form sheets
The apical surface is the free surface of the tissue
The lower surface of the epithelium rests on a basement membrane
Avascular (no blood supply)
Regenerate easily if well nourished
Classification of Epithelia

Number of cell layers
o Simple—one layer
o Stratified—more than one layer
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Classification of Epithelia

Shape of cells
o Squamous
 Flattened, like fish scales
o Cuboidal
 Cube-shaped, like dice
o Columnar
 Column-like
Simple Epithelia

Simple squamous
o Single layer of flat cells
o Location—usually forms membranes
 Lines air sacs of the lungs
 Forms walls of capillaries
 Forms serous membranes (serosae) that line and cover organs in
ventral cavity
o Functions in diffusion, filtration, or secretion in membranes
Simple Epithelia

Simple cuboidal
o Single layer of cube-like cells
o Locations:
 Common in glands and their ducts
 Forms walls of kidney tubules
 Covers the surface of ovaries
o Functions in secretion and absorption; ciliated types propel mucus or
reproductive cells
Simple Epithelia

Simple columnar
o Single layer of tall cells
 Goblet cells secrete mucus
o Location:
 Lines digestive tract from stomach to anus
 Mucous membranes (mucosae) line body cavities opening to the
exterior
o Functions in secretion and absorption; ciliated types propel mucus or
reproductive cells
Simple Epithelia

Pseudostratified columnar
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o All cells rest on a basement membrane
o Single layer, but some cells are shorter than others giving a false (pseudo)
impression of stratification
o Location:
 Respiratory tract, where it is ciliated and known as pseudostratified
ciliated columnar epithelium
o Functions in absorption or secretion
Stratified Epithelia

Stratified squamous
o Named for cells present at the free (apical) surface, which are flattened
o Functions as a protective covering where friction is common
o Locations—lining of the:
 Skin (outer portion)
 Mouth
 Esophagus
Stratified Epithelia



Stratified cuboidal—two layers of cuboidal cells; functions in protection
Stratified columnar—surface cells are columnar, and cells underneath vary in
size and shape; functions in protection
Stratified cuboidal and columnar
o Rare in human body
o Found mainly in ducts of large glands
Stratified Epithelia

Transitional epithelium
o Composed of modified stratified squamous epithelium
o Shape of cells depends upon the amount of stretching
o Functions in stretching and the ability to return to normal shape
o Locations: urinary system organs
Glandular Epithelium

Gland
o One or more cells responsible for secreting a particular product
o Secretions contain protein molecules in an aqueous (water-based) fluid
o Secretion is an active process
Glandular Epithelium

Two major gland types
o Endocrine gland
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


Ductless; secretions diffuse into blood vessels
All secretions are hormones
Examples include thyroid, adrenals, and pituitary
Glandular Epithelium

Two major gland types
o Exocrine gland
 Secretions empty through ducts to the epithelial surface
 Include sweat and oil glands, liver, and pancreas
 Includes both internal and external glands
Connective Tissue



Found everywhere in the body
Includes the most abundant and widely distributed tissues
Functions:
o Provides protection
o Binds body tissues together
o Supports the body
Connective Tissue Characteristics


Variations in blood supply
o Some tissue types are well vascularized
o Some have a poor blood supply or are avascular
Extracellular matrix
o Nonliving material that surrounds living cells
Extracellular Matrix

Two main elements
1. Ground substance—mostly water along with adhesion proteins and
polysaccharide molecules
2. Fibers
 Produced by the cells
 Three types:
1. Collagen (white) fibers
2. Elastic (yellow) fibers
3. Reticular fibers (a type of collagen)
Connective Tissue Types

From most rigid to softest, or most fluid:
o Bone
o Cartilage
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o Dense connective tissue
o Loose connective tissue
o Blood
Connective Tissue Types

Bone (osseous tissue)
o Composed of:
 Osteocytes (bone cells) sitting in lacunae (cavities)
 Hard matrix of calcium salts
 Large numbers of collagen fibers
o Functions to protect and support the body
Connective Tissue Types

Cartilage
o Less hard and more flexible than bone
o Found in only a few places in the body
o Chondrocyte (cartilage cell) is the major cell type
Connective Tissue Types

Hyaline cartilage
o Hyaline cartilage is the most widespread type of cartilage
 Composed of abundant collagen fibers and a rubbery matrix
 Locations:
• Larynx
• Entire fetal skeleton prior to birth
• Epiphyseal plates
o Functions as a more flexible skeletal element than bone
Connective Tissue Types


Elastic cartilage (not pictured)
o Provides elasticity
o Location:
 Supports the external ear
Fibrocartilage
o Highly compressible
o Location:
 Forms cushionlike discs between vertebrae of the spinal column
Connective Tissue Types

Dense connective tissue (dense fibrous tissue)
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o Main matrix element is collagen fiber
o Fibroblasts are cells that make fibers
o Locations:
 Tendons—attach skeletal muscle to bone
 Ligaments—attach bone to bone at joints and are more elastic than
tendons
 Dermis—lower layers of the skin
Connective Tissue Types

Loose connective tissue types
o Areolar tissue
 Most widely distributed connective tissue
 Soft, pliable tissue like “cobwebs”
 Functions as a universal packing tissue and “glue” to hold organs in
place
 Layer of areolar tissue called lamina propria underlies all
membranes
 All fiber types form a loose network
 Can soak up excess fluid (causes edema)
Connective Tissue Types

Loose connective tissue types
o Adipose tissue
 Matrix is an areolar tissue in which fat globules predominate
 Many cells contain large lipid deposits with nucleus to one side
(signet ring cells)
 Functions
• Insulates the body
• Protects some organs
• Serves as a site of fuel storage
Connective Tissue Types

Loose connective tissue types
o Reticular connective tissue
 Delicate network of interwoven fibers with reticular cells (like
fibroblasts)
 Locations:
• Forms stroma (internal framework) of organs, such as these
lymphoid organs:
o Lymph nodes
o Spleen
o Bone marrow
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Connective Tissue Types

Blood (vascular tissue)
o Blood cells surrounded by fluid matrix known as blood plasma
o Soluble fibers are visible only during clotting
o Functions as the transport vehicle for the cardiovascular system, carrying:
 Nutrients
 Wastes
 Respiratory gases
Muscle Tissue


Function is to contract, or shorten, to produce movement
Three types:
1. Skeletal muscle
2. Cardiac muscle
3. Smooth muscle
Muscle Tissue Types

Skeletal muscle
o Voluntarily (consciously) controlled
o Attached to the skeleton and pull on bones or skin
o Produces gross body movements or facial expressions
o haracteristics of skeletal muscle cells
 Striations (stripes)
 Multinucleate (more than one nucleus)
 Long, cylindrical shape
Muscle Tissue Types

Cardiac muscle
o Involuntarily controlled
o Found only in the heart
o Pumps blood through blood vessels
o Characteristics of cardiac muscle cells
 Striations
 Uninucleate, short, branching cells
 Intercalated discs contain gap junctions to connect cells together
Muscle Tissue Types

Smooth (visceral) muscle
o Involuntarily controlled
o Found in walls of hollow organs such as stomach, uterus, and blood
vessels
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o Peristalsis, a wavelike activity, is a typical activity
o Characteristics of smooth muscle cells
 No visible striations
 Uninucleate
 Spindle-shaped cells
Nervous Tissue



Composed of neurons and nerve support cells
Function is to receive and conduct electrochemical impulses to and from body
parts
o Irritability
o Conductivity
Support cells called neuroglia insulate, protect, and support neurons
Summary of Tissues

Figure 3.22 summarizes the tissue types and functions in the body
Tissue Repair (Wound Healing)

Tissue repair (wound healing) occurs in two ways:
o Regeneration
 Replacement of destroyed tissue by the same kind of cells
o Fibrosis
 Repair by dense (fibrous) connective tissue (scar tissue)
Tissue Repair (Wound Healing)

Whether regeneration or fibrosis occurs depends on:
o Type of tissue damaged
o Severity of the injury

Clean cuts (incisions) heal more successfully than ragged tears of the tissue
Events in Tissue Repair


Inflammation
o Capillaries become very permeable
o Clotting proteins migrate into the area from the bloodstream
o A clot walls off the injured area
Granulation tissue forms
o Growth of new capillaries
o Phagocytes dispose of blood clot and fibroblasts
o Rebuild collagen fibers
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Events in Tissue Repair

Regeneration of surface epithelium
o Scab detaches
o Whether scar is visible or invisible depends on severity of wound
Regeneration of Tissues



Tissues that regenerate easily
o Epithelial tissue (skin and mucous membranes)
o Fibrous connective tissues and bone
Tissues that regenerate poorly
o Skeletal muscle
Tissues that are replaced largely with scar tissue
o Cardiac muscle
o Nervous tissue within the brain and spinal cord
Development Aspects of Cells and Tissues





Growth through cell division continues through puberty
Cell populations exposed to friction (such as epithelium) replace lost cells
throughout life
Connective tissue remains mitotic and forms repair (scar) tissue
With some exceptions, muscle tissue becomes amitotic by the end of puberty
Nervous tissue becomes amitotic shortly after birth.
Developmental Aspects of Cells and Tissues


Injury can severely handicap amitotic tissues
The cause of aging is unknown, but chemical and physical insults, as well as
genetic programming, have been proposed as possible causes
Developmental Aspects of Cells and Tissues



Neoplasms, both benign and cancerous, represent abnormal cell masses in
which normal controls on cell division are not working
Hyperplasia (increase in size) of a tissue or organ may occur when tissue is
strongly stimulated or irritated
Atrophy (decrease in size) of a tissue or organ occurs when the organ is no
longer stimulated normally
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Body Membranes


Functions of body membranes
o Cover body surfaces
o Line body cavities
o Form protective sheets around organs
Classified according to tissue types
Classification of Body Membranes


Epithelial membranes
o Cutaneous membranes
o Mucous membranes
o Serous membranes
Connective tissue membranes
o Synovial membranes
Cutaneous Membrane


Cutaneous membrane = skin
o Dry membrane
o Outermost protective boundary
Superficial epidermis is composed of keratinized stratified squamous epithelium
o Underlying dermis is mostly dense (fibrous) connective tissue
Mucous Membranes




Surface epithelium type depends on site
o Stratified squamous epithelium (mouth, esophagus)
o Simple columnar epithelium (rest of digestive tract)
Underlying loose connective tissue (lamina propria)
Lines all body cavities that open to the exterior body surface
Moist membranes adapted for absorption or secretion
Serous Membranes (Serosa)




Surface is a layer of simple squamous epithelium
Underlying layer is a thin layer of areolar connective tissue
Lines open body cavities that are closed to the exterior of the body
Serous membranes occur in pairs separated by serous fluid
o Visceral layer covers the outside of the organ
o Parietal layer lines a portion of the wall of ventral body cavity
Serous Membranes

Specific serous membranes
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o Peritoneum
 Abdominal cavity
o Pleura
 Around the lungs
o Pericardium
 Around the heart
Connective Tissue Membrane

Synovial membrane
o Connective tissue only
o Lines fibrous capsules surrounding joints
 Lines bursae
 Lines tendon sheaths
o Secretes a lubricating fluid
Integumentary System

Integumentary system includes:
o Skin (cutaneous membrane)
o Skin derivatives
 Sweat glands
 Oil glands
 Hair
 Nails
Skin (Integument) Functions

Protects deeper tissues from:
o Mechanical damage (bumps)
o Chemical damage (acids and bases)
o Bacterial damage
o Ultraviolet radiation (sunlight)
o Thermal damage (heat or cold)
o Desiccation (drying out)
 Keratin protects the skin from water loss
Skin Functions




Aids in loss or retention of body heat as controlled by the nervous system
Aids in excretion of urea and uric acid
Synthesizes vitamin D
Cutaneous sensory receptors detect touch, temperature, pressure, and pain
Skin Structure

Epidermis—outer layer
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
o
o
o
o
Dermis
o
Stratified squamous epithelium
Cornified or keratinized (hardened by keratin) to prevent water loss
Avascular
Most cells are keratinocytes
Dense connective tissue
Skin Structure

Subcutaneous tissue (hypodermis) is deep to dermis
o Not technically part of the skin
o Anchors skin to underlying organs
o Composed mostly of adipose tissue
o Serves as a shock absorber and insulates deeper tissues
Layers of the Epidermis




The epidermis is composed of up to five layers
The epidermis is avascular
Most of the cells in the epidermis are keratinocytes
o Keratin, a fibrous protein, makes the epidermis tough
The layers are covered, next, from deepest to most superficial
Layers of the Epidermis


Stratum basale (stratum germinativum)
o Deepest layer of epidermis
o Lies next to dermis
o Wavy borderline with the dermis anchors the two together
o Cells undergoing mitosis
o Daughter cells are pushed upward to become the more superficial layers
Stratum spinosum
Layers of the Epidermis



Stratum granulosum
Stratum lucidum
o Formed from dead cells of the deeper strata
o Occurs only in thick, hairless skin of the palms of hands and soles of feet
Stratum corneum
o Outermost layer of epidermis
o Shingle-like dead cells are filled with keratin (protective protein prevents
water loss from skin)
Layers of the Epidermis

Summary of layers from deepest to most superficial
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o
o
o
o
o
Stratum basale
Stratum spinosum
Stratum granulosum
Stratum lucidum (thick, hairless skin only)
Stratum corneum
Melanin





Pigment (melanin) produced by melanocytes
Color is yellow to brown to black
Melanocytes are mostly in the stratum basale
Melanin accumulates in membrane-bound granules called melanosomes
Amount of melanin produced depends upon genetics and exposure to sunlight
Epidermal Dendritic Cells & Merkel Cells


Epidermal dendritic cells
o Alert and activate immune cells to a threat (bacterial or viral invasion)
Merkel cells
o Associated with sensory nerve endings
o Serve as touch receptors called Merkel discs
Dermis

Two layers
1. Papillary layer (upper dermal region)
o Projections called dermal papillae
 Some contain capillary loops
 Others house pain receptors (free nerve endings) and touch
receptors
 Fingerprints are identifying films of sweat
Dermis

Two layers
2. Reticular layer (deepest skin layer)
o Blood vessels
o Sweat and oil glands
o Deep pressure receptors (lamellar corpuscles)
Dermis

Overall dermis structure
o Collagen and elastic fibers located throughout the dermis
 Collagen fibers give skin its toughness
 Elastic fibers give skin elasticity
o Blood vessels play a role in body temperature regulation
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o Nerve supply sends messages to the central nervous system
Skin Color

Three pigments contribute to skin color:
1. Melanin
o Yellow, reddish brown, or black pigments
2. Carotene
o Orange-yellow pigment from some vegetables
3. Hemoglobin
o Red coloring from blood cells in dermal capillaries
o Oxygen content determines the extent of red coloring
Alterations in Skin Color




Redness (erythema)—due to embarrassment, inflammation, hypertension, fever, or
allergy
Pallor (blanching)—due to emotional stress (such as fear), anemia, low blood
pressure, impaired blood flow to an area
Jaundice (yellowing)—liver disorder
Bruises (black and blue marks)—hematomas
Appendages of the Skin




Cutaneous glands are all exocrine glands
o Sebaceous glands
o Sweat glands
Hair
Hair follicles
Nails
Appendages of the Skin

Sebaceous (oil) glands
o Produce sebum (oil)
 Lubricant for skin
 Prevents brittle hair
 Kills bacteria
o Most have ducts that empty into hair follicles; others open directly onto skin
surface
o Glands are activated at puberty
Appendages of the Skin

Sweat (sudoriferous) glands
o Produce sweat
o Widely distributed in skin
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Appendages of the Skin

Two types of sudoriferous glands
1. Eccrine glands
o Open via duct to pore on skin surface
o Produce sweat
Appendages of the Skin

Sweat:
o Composition
 Mostly water
 Salts and vitamin C
 Some metabolic waste
 Fatty acids and proteins (apocrine only)
o Function
 Helps dissipate excess heat
 Excretes waste products
 Acidic nature inhibits bacteria growth
o Odor is from associated bacteria
Appendages of the Skin

Two types of sudoriferous glands
2. Apocrine glands
o Ducts empty into hair follicles
o Begin to function at puberty
o Release sweat that also contains fatty acids and proteins (milky or yellowish
color)
Appendages of the Skin

Hair
o
o
o
o
o
o
Produced by hair follicle
Root is enclosed in the follicle
Shaft projects from the surface of the scalp or skin
Consists of hard keratinized epithelial cells
Melanocytes provide pigment for hair color
Hair grows in the matrix of the hair bulb in stratum basale
Appendages of the Skin

Hair anatomy
o Central medulla
o Cortex surrounds medulla
o Cuticle on outside of cortex
 Most heavily keratinized region of the hair
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Appendages of the Skin

Associated hair structures
o Hair follicle
 Dermal and epidermal sheath surround hair root
o Arrector pili muscle
 Smooth muscle
 Pulls hairs upright when person is cold or frightened
o Sebaceous gland
o Sudoriferous gland
Appendages of the Skin

Notice how the scale-like cells of the cuticle overlap one another in this hair shaft
image (660×)
Appendages of the Skin

Nails
o Scale-like modifications of the epidermis
 Heavily keratinized
o Stratum basale extends beneath the nail bed
 Responsible for growth
o Lack of pigment makes them colorless
Appendages of the Skin

Nail structures
o Free edge
o Body is the visible attached portion
o Nail folds are skin folds that overlap the edges of the nail
o Growth occurs from nail matrix
o Root of nail is embedded in skin
o Cuticle is the proximal nail fold that projects onto the nail body
Skin Homeostatic Imbalances

Burns
o Tissue damage and cell death caused by heat, electricity, UV radiation, or
chemicals
o Associated dangers
 Dehydration
 Electrolyte imbalance
 Circulatory shock
o Result in loss of body fluids and invasion of bacteria
Rule of Nines
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


Way to determine the extent of burns
Body is divided into 11 areas for quick estimation
Each area represents about 9 percent of total body surface area
o The area surrounding the genitals (the perineum) represents 1 percent of
body surface area
Severity of Burns



First-degree burns (partial-thickness burn)
o Only epidermis is damaged
o Skin is red and swollen
Second-degree burns (partial-thickness burn)
o Epidermis and upper dermis are damaged
o Skin is red with blisters
Third-degree burns (full-thickness burn)
o Destroys entire skin layer; burned area is painless
o Requires skin grafts
o Burn is gray-white or black
Critical Burns

Burns are considered critical if
o Over 25 percent of body has second-degree burns
o Over 10 percent of the body has third-degree burns
o There are third-degree burns of the face, hands, or feet
Skin Homeostatic Imbalances

Infections
o Athlete’s foot (tinea pedis)
 Caused by fungal infection
o Boils and carbuncles
 Caused by bacterial infection
o Cold sores
 Caused by virus
Skin Homeostatic Imbalances

Infections and allergies
o Contact dermatitis
 Exposures cause allergic reaction
o Impetigo
 Caused by bacterial infection
o Psoriasis
 Cause is unknown
 Triggered by trauma, infection, stress
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Skin Cancer



Cancer—abnormal cell mass
Classified two ways
1. Benign
o Does not spread (encapsulated)
2. Malignant
o Metastasizes (moves) to other parts of the body
Skin cancer is the most common type of cancer
Skin Cancer Types

Basal cell carcinoma
o Least malignant
o Most common type
o Arises from stratum basale
Skin Cancer Types

Squamous cell carcinoma
o Metastasizes to lymph nodes if not removed
o Early removal allows a good chance of cure
o Believed to be sun-induced
o Arises from stratum spinosum
Skin Cancer Types

Malignant melanoma
o Most deadly of skin cancers
o Cancer of melanocytes
o Metastasizes rapidly to lymph and blood vessels
o Detection uses ABCD rule
ABCD Rule




A = Asymmetry
o Two sides of pigmented mole do not match
B = Border irregularity
o Borders of mole are not smooth
C = Color
o Different colors in pigmented area
D = Diameter
o Spot is larger than 6 mm in diameter
Developmental Aspects of Skin


In youth, skin is thick, resilient, and well hydrated
With aging, skin loses elasticity and thins
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

Skin cancer is a major threat to skin exposed to excessive sunlight
Balding and/or graying occurs with aging; both are genetically determined; other
factors that may contribute include drugs and emotional stress
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The Skeletal System


Two subdivisions of the skeleton
1. Axial skeleton
2. Appendicular skeleton
Parts of the skeletal system
o Bones (skeleton)
o Joints
o Cartilages
o Ligaments
Functions of Bones





Support the body
Protect soft organs
o Skull and vertebrae protect brain and spinal cord
o Rib cage protects thoracic cavity organs
Attached skeletal muscles allow movement
Store minerals and fats
o Calcium and phosphorus
o Fat in the internal marrow cavity
Blood cell formation (hematopoiesis)
Bones of the Human Body


The adult skeleton has 206 bones
Two basic types of bone tissue
1. Compact bone
 Dense, smooth, and homogeneous
2. Spongy bone
 Small needle-like pieces of bone
 Many open spaces
Classification of Bones
Bones are classified on the basis of shape, as:
o
o
o
o
Long
Short
Flat
Irregular
Classification of Bones

Long bones
o Typically longer than they are wide
o Shaft with heads situated at both ends
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o Contain mostly compact bone
o All of the bones of the limbs (except wrist, ankle, and kneecap bones) are long
bones
o Examples:
 Femur
 Humerus
Classification of Bones

Short bones
o Generally cube-shaped
o Contain mostly spongy bone
o Include bones of the wrist and ankle
o Sesamoid bones are a type of short bone that form within tendons (patella)
o Examples:
 Carpals
 Tarsals
Classification of Bones

Flat bones
o Thin, flattened, and usually curved
o Two thin layers of compact bone surround a layer of spongy bone
o Examples:
 Skull
 Ribs
 Sternum
Classification of Bones

Irregular bones
o Irregular shape
o Do not fit into other bone classification categories
o Examples:
 Vertebrae
 Hip bones
Anatomy of a Long Bone


Diaphysis
o Shaft
o Makes up most of bone’s length
o Composed of compact bone
Periosteum
o Outside covering of the diaphysis
o Fibrous connective tissue membrane
o Perforating (Sharpey’s) fibers secure periosteum to underlying bone
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Anatomy of a Long Bone


Epiphysis
o Ends of the bone
o Composed mostly of spongy bone enclosed by thin layer of compact bone
Articular cartilage
o Covers the external surface of the epiphyses
o Made of hyaline cartilage
o Decreases friction at joint surfaces
Anatomy of a Long Bone


Epiphyseal plate
o Flat plate of hyaline cartilage seen in young, growing bone
o Causes lengthwise growth of a long bone
Epiphyseal line
o Remnant of the epiphyseal plate
o Seen in adult bones
Anatomy of a Long Bone


Marrow (medullary) cavity
o Cavity inside the shaft
o Contains yellow marrow (mostly fat) in adults
o Contains red marrow for blood cell formation in infants
In adults, red marrow is situated in cavities of spongy bone and epiphyses of some
long bones
Bone Markings


Surface features of bones
o Sites of attachments for muscles, tendons, and ligaments
o Passages for nerves and blood vessels
Categories of bone markings
o Projections or processes—grow out from the bone surface
 Terms often begin with “T”
o Depressions or cavities—indentations
 Terms often begin with “F”
Microscopic Anatomy of Compact Bone



Osteocytes are situated within cavities known as lacunae
Lacunae are arranged in concentric rings called lamellae
Lamellae are rings situated around the central (Haversian) canal
Microscopic Anatomy of Bone

Central (Haversian) canal
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
o Opening in the center of an osteon
o Runs lengthwise through bone
o Carries blood vessels and nerves
Osteon (Haversian system)
o A unit of bone containing central canal and matrix rings
Microscopic Anatomy of Bone


Canaliculi
o Tiny canals
o Radiate from the central canal to lacunae
o Form a transport system connecting all bone cells to a nutrient supply
Perforating (Volkmann’s) canal
o Canal perpendicular to the central canal
o Carries blood vessels and nerves
Bone Components


Organic parts of the matrix make bone flexible
Calcium salts deposited in the matrix make bone hard
Bone Formation and Growth

Ossification
o Process of bone formation
o Occurs on hyaline cartilage models or fibrous membranes
o Long bone growth involves two major phases
Bone Formation and Growth
Two major phases of ossification in long bones
1. Osteoblasts
 Bone-forming cells
 Cover hyaline cartilage model
2. Enclosed cartilage is digested away, opening up a medullary cavity
Bone Formation and Growth



By birth, most cartilage is converted to bone except for two regions in a long bone:
o Articular cartilages
o Epiphyseal plates
New cartilage is formed continuously on external face of these two cartilages
Old cartilage is broken down and replaced by bony matrix
Bone Formation and Growth

Bones grow in length and width
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

o Appositional growth
 Growth in diameter
Controlled by hormones such as growth hormone
Epiphyseal plates are converted to bone during adolescence
o Growth in length ends
Bone Remodeling


Bones are lengthened until growth stops
Bones are remodeled throughout life in response to two factors:
1. Blood calcium levels
2. Pull of gravity and muscles on the skeleton
Bone Remodeling


Parathyroid hormone (PTH)
o Released when blood calcium levels are low
o Activates osteoclasts (bone-destroying cells)
o Osteoclasts break down bone and release calcium ions into the blood
Hypercalcemia (high blood calcium levels) prompts calcium storage to bones
Bone Fractures


Fracture: break in a bone
Types of bone fractures
o Closed (simple) fracture: break that does not penetrate the skin
o Open (compound) fracture: broken bone penetrates through the skin
Bone Fractures

Bone fractures are treated by reduction and immobilization
o Closed reduction: bones are manually coaxed into position by physician’s
hands
o Open reduction: bones are secured with pins or wires during surgery
Repair of Bone Fractures




Hematoma (blood-filled swelling) is formed
Fibrocartilage callus forms
o Cartilage matrix, bony matrix, collagen fibers splint the broken bone
Bony callus replaces the fibrocartilage callus
o Osteoblasts and osteoclasts migrate in
Bone remodeling occurs in response to mechanical stresses
Common Types of Fractures

Comminuted: bone breaks into many fragments
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




Compression: bone is crushed
Depressed: broken bone portion is pressed inward
Impacted: broken bone ends are forced into each other
Spiral: ragged break occurs when excessive twisting forces are applied to a bone
Greenstick: bone breaks incompletely
The Axial Skeleton


Forms the longitudinal axis of the body
Divided into three parts
1. Skull
2. Vertebral column
3. Bony thorax
The Skull



Two sets of bones
1. Cranium bones enclose the brain
2. Facial bones
 Hold eyes in anterior position
 Allow facial muscles to express feelings
Bones are joined by sutures
Only the mandible is attached by a freely movable joint
The Skull

8 cranial bones protect the brain
1. Frontal bone
2. Occipital bone
3. Ethmoid bone
4. Sphenoid bone
5–6. Parietal bones (pair)
7–8. Temporal bones (pair)
The Skull

There are 14 facial bones. All are paired except for the single mandible and vomer.
1–2. Maxillae
3–4. Zygomatics
5–6. Palatines
7–8. Nasals
9–10. Lacrimals
11–12. Inferior nasal conchae
13. Mandible
14. Vomer
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Paranasal Sinuses


Hollow portions of bones surrounding the nasal cavity
Functions of paranasal sinuses
o Lighten the skull
o Amplify sounds made as we speak
The Hyoid Bone




Closely related to mandible and temporal bones
The only bone that does not articulate with another bone
Serves as a movable base for the tongue
Aids in swallowing and speech
The Fetal Skull


The fetal skull is large compared to the infant’s total body length
o Fetal skull is 1/4 body length compared to adult skull, which is 1/8 body length
Fontanels are fibrous membranes connecting the cranial bones
o Allow skull compression during birth
o Allow the brain to grow during later pregnancy and infancy
o Convert to bone within 24 months after birth
Vertebral Column (Spine)


Vertebral column provides axial support
o Extends from skull to the pelvis
26 single vertebral bones are separated by intervertebral discs
o 7 cervical vertebrae are in the neck
o 12 thoracic vertebrae are in the chest region
o 5 lumbar vertebrae are associated with the lower back
Vertebral Column (Spine)

9 vertebrae fuse to form two composite bones
o Sacrum formed by the fusion of 5 vertebrae
o Coccyx (tailbone) formed by the fusion of 3 to 5 vertebrae
Vertebral Column (Spine)


Primary curvatures
o Spinal curvatures of the thoracic and sacral regions
o Present from birth
o Form a C-shaped curvature as in newborns
Secondary curvatures
o Spinal curvatures of the cervical and lumbar regions
o Develop after birth
o Form an S-shaped curvature as in adults
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Vertebral Column (Spine)

Parts of a typical vertebra
o Body (centrum)
o Vertebral arch
 Pedicle
 Lamina
o Vertebral foramen
o Transverse processes
o Spinous process
o Superior and inferior articular processes
The Bony Thorax


Forms a cage to protect major organs
Consists of three parts
1. Sternum
2. Ribs
 True ribs (pairs 1–7)
 False ribs (pairs 8–12)
 Floating ribs (pairs 11–12)
3. Thoracic vertebrae
The Appendicular Skeleton

Composed of 126 bones
o Limbs (appendages)
o Pectoral girdle
o Pelvic girdle
The Pectoral (Shoulder) Girdle


Composed of two bones that attach the upper limb to the axial skeletal
1. Scapula
2. Clavicle
Pectoral girdle (2)
o Light, poorly reinforced girdle
o Allows the upper limb a great deal of freedom
Bones of the Upper Limbs

Humerus
o Forms the arm
o Single bone
o Proximal end articulation
 Head articulates with the glenoid cavity of the scapula
o Distal end articulation
 Trochlea and capitulum articulate with the bones of the forearm
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Bones of the Upper Limbs

The forearm has two bones
1. Ulna—medial bone in anatomical position
 Proximal end articulation
o Coronoid process and olecranon articulate with the humerus
2. Radius—lateral bone in anatomical position
 Proximal end articulation
o Head articulates with the capitulum of the humerus
Bones of the Upper Limbs

Hand
o Carpals—wrist
 8 bones arranged in two rows of 4 bones in each hand
o Metacarpals—palm
 5 per hand
o Phalanges—fingers and thumb
 14 phalanges in each hand
 In each finger, there are 3 bones
 In the thumb, there are only 2 bones
Bones of the Pelvic Girdle




Formed by 2 coxal (ossa coxae) bones
Composed of three pairs of fused bones
1. Ilium
2. Ischium
3. Pubis
Pelvic girdle = 2 coxal bones, sacrum
Bony pelvis = 2 coxal bones, sacrum, coccyx
Bones of the Pelvic Girdle


The total weight of the upper body rests on the pelvis
Pelvis protects several organs
o Reproductive organs
o Urinary bladder
o Part of the large intestine
Gender Differences of the Pelvis

The female’s pelvis:
o Inlet is larger and more circular
o Pelvis as a whole is shallower, and the bones are lighter and thinner
o Ilia flare more laterally
o Sacrum is shorter and less curved
o Ischial spines are shorter and farther apart; thus, the outlet is larger
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o Pubic arch is more rounded because the angle of the pubic arch is greater
Bones of the Lower Limbs

Femur—thigh bone
o The heaviest, strongest bone in the body
o Proximal end articulation
 Head articulates with the acetabulum of the coxal (hip) bone
o Distal end articulation
 Lateral and medial condyles articulate with the tibia in the lower leg
Bones of the Lower Limbs

The lower leg has two bones
1. Tibia—shinbone; larger and medially oriented
 Proximal end articulation
o Medial and lateral condyles articulate with the femur to form the
knee joint
2. Fibula—thin and sticklike; lateral to the tibia
 Has no role in forming the knee joint
Bones of the Lower Limbs

The foot
o Tarsals—7 bones
 Two largest tarsals
o Calcaneus (heel bone)
o Talus
o Metatarsals—5 bones form the sole of the foot
o Phalanges—14 bones form the toes
Arches of the Foot

Bones of the foot are arranged to form three strong arches
o Two longitudinal
o One transverse
Joints



Joints are articulations
o Two or more bones meet
Functions of joints
o Hold bones together
o Allow for mobility
Two ways joints are classified
o Functionally
o Structurally
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Functional Classification of Joints



Synarthroses
o Immovable joints
Amphiarthroses
o Slightly movable joints
Diarthroses
o Freely movable joints
Structural Classification of Joints



Fibrous joints
o Generally immovable
Cartilaginous joints
o Immovable or slightly movable
Synovial joints
o Freely movable
Fibrous Joints


Bones united by fibrous tissue
Types
o Sutures
 Immobile
o Syndesmoses
 Allow more movement than sutures but still immobile
 Example: Distal end of tibia and fibula
o Gomphosis
 Immobile
Cartilaginous Joints


Bones connected by fibrocartilage
Types
o Synchrondrosis
 Immobile
o Symphysis
 Slightly movable
 Example: Pubic symphysis, intervertebral joints
Synovial Joints



Articulating bones are separated by a joint cavity
Synovial fluid is found in the joint cavity
Four distinguishing features of synovial joints
1. Articular cartilage
3. Articular capsule
4. Joint cavity
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5. Reinforcing ligaments
Synovial Joints


Bursae—flattened fibrous sacs
o Lined with synovial membranes
o Filled with synovial fluid
o Not actually part of the joint
Tendon sheath
o Elongated bursa that wraps around a tendon
Synovial Joints

Types of synovial joints based on shape:
o Plane joint
o Hinge joint
o Pivot joint
o Condylar joint
o Saddle joint
o Ball-and-socket joint
Inflammatory Conditions Associated with Joints



Bursitis—inflammation of a bursa, usually caused by a blow or friction
Tendonitis—inflammation of tendon sheaths
Arthritis—inflammatory or degenerative diseases of joints
o Over 100 different types
o The most widespread crippling disease in the United States
o Initial symptoms: pain, stiffness, swelling of the joint
Clinical Forms of Arthritis


Osteoarthritis (OA)
o Most common chronic arthritis
o Probably related to normal aging processes
Rheumatoid arthritis (RA)
o An autoimmune disease—the immune system attacks the joints
o Symptoms begin with bilateral inflammation of certain joints
o Often leads to deformities
Clinical Forms of Arthritis

Gouty arthritis (gout)
o Inflammation of joints is caused by a deposition of uric acid crystals from the
blood
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o Can usually be controlled with diet
o More common in men
Developmental Aspects of the Skeletal System

Fontanels
o Allow brain growth and ease birth passage
o Present in the skull at birth
o Completely replaced with bone within 2 years after birth
Developmental Aspects of the Skeletal System

Growth of cranium after birth is related to brain growth
o Increase in size of the facial skeleton follows tooth development and
enlargement of the respiratory passageways.
Skeletal Changes Throughout Life


Fetus
o
o
o
Birth
o
Long bones are formed of hyaline cartilage
Flat bones begin as fibrous membranes
Flat and long bone models are converted to bone
Fontanels remain until around age 2
Skeletal Changes Throughout Life


Adolescence
o Epiphyseal plates become ossified, and long bone growth ends
Size of cranium in relationship to body
o 2 years old—skull is larger in proportion to the body compared to that of an
adult
o 8 or 9 years old—skull is near adult size and proportion
o Between ages 6 and 11, the face grows out from the skull
Skeletal Changes Throughout Life

Curvatures of the spine
o Primary curvatures are present at birth and are convex posteriorly
o Secondary curvatures are associated with a child’s later development and are
convex anteriorly
o Abnormal spinal curvatures (scoliosis and lordosis) are often congenital
Skeletal Changes Throughout Life

Osteoporosis
o Bone-thinning disease afflicting
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 50 percent of women over age 65
 20 percent of men over age 70
o Disease makes bones fragile, and bones can easily fracture
o Vertebral collapse results in kyphosis (also known as “dowager’s hump”)
o Estrogen aids in health and normal density of a female skeleton
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The Muscular System


Muscles are responsible for all types of body movement
Three basic muscle types are found in the body
1. Skeletal muscle
2. Cardiac muscle
3. Smooth muscle
Characteristics of Muscles



Skeletal and smooth muscle cells are elongated (muscle cell = muscle fiber)
Contraction and shortening of muscles is due to the movement of microfilaments
All muscles share some terminology
o Prefixes myo and mys refer to “muscle”
o Prefix sarco refers to “flesh”
Skeletal Muscle Characteristics




Most are attached by tendons to bones
Cells are multinucleate
Striated—have visible banding
Voluntary—subject to conscious control
Connective Tissue Wrappings of Skeletal Muscle

Cells are surrounded and bundled by connective tissue
o Endomysium—encloses a single muscle fiber
o Perimysium—wraps around a fascicle (bundle) of muscle fibers
o Epimysium—covers the entire skeletal muscle
o Fascia—on the outside of the epimysium
Skeletal Muscle Attachments

Epimysium blends into a connective tissue attachment
o Tendons—cordlike structures
 Mostly collagen fibers
 Often cross a joint because of their toughness and small size
o Aponeuroses—sheetlike structures
 Attach muscles indirectly to bones, cartilages, or connective tissue
coverings
Skeletal Muscle Attachments

Sites of muscle attachment
o Bones
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o Cartilages
o Connective tissue coverings
Smooth Muscle Characteristics





Lacks striations
Spindle-shaped cells
Single nucleus
Involuntary—no conscious control
Found mainly in the walls of hollow visceral organs (such as stomach, urinary bladder,
respiratory passages)
Cardiac Muscle Characteristics






Striations
Usually has a single nucleus
Branching cells
Joined to another muscle cell at an intercalated disc
Involuntary
Found only in the walls of the heart
Skeletal Muscle Functions




Produce movement
Maintain posture
Stabilize joints
Generate heat
Microscopic Anatomy of Skeletal Muscle


Sarcolemma—specialized plasma membrane
Myofibrils—long organelles inside muscle cell
o Light (I) bands and dark (A) bands give the muscle its striped appearance
Microscopic Anatomy of Skeletal Muscle

Banding pattern
o I band = light band
 Contains only thin filaments
 Z disc is a midline interruption
o A band = dark band
 Contains the entire length of the thick filaments
 H zone is a lighter central area
 M line is in center of H zone
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Microscopic Anatomy of Skeletal Muscle


Sarcomere—contractile unit of a muscle fiber
Organization of the sarcomere
o Myofilaments produce banding (striped) pattern
 Thick filaments = myosin filaments
 Thin filaments = actin filaments
Microscopic Anatomy of Skeletal Muscle

Thick filaments = myosin filaments
o Composed of the protein myosin
o Contain ATPase enzymes
o Possess myosin heads
o Heads are known as cross bridges when they link thick and thin filaments
during contraction
Microscopic Anatomy of Skeletal Muscle


Thin filaments = actin filaments
o Composed of the contractile protein actin
o Actin is anchored to the Z disc
At rest, within the A band there is a zone that lacks actin filaments
o Called the H zone
Microscopic Anatomy of Skeletal Muscle

Sarcoplasmic reticulum (SR)
o Specialized smooth endoplasmic reticulum
o Stores and releases calcium
o Surrounds the myofibril
Stimulation and Contraction of Single Skeletal Muscle Cells




Irritability (also called responsiveness)—ability to receive and respond to a stimulus
Contractility—ability to shorten when an adequate stimulus is received
Extensibility—ability of muscle cells to be stretched
Elasticity—ability to recoil and resume resting length after stretching
The Nerve Stimulus and Action Potential


Skeletal muscles must be stimulated by a motor neuron (nerve cell) to contract
Motor unit—one motor neuron and all the skeletal muscle cells stimulated by that
neuron
The Nerve Stimulus and Action Potential
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

Neuromuscular junction
o Association site of axon terminal of the motor neuron and sarcolemma of a
muscle
Neurotransmitter
o Chemical released by nerve upon arrival of nerve impulse in the axon terminal
o Acetylcholine (ACh) is the neurotransmitter that stimulates skeletal muscle
The Nerve Stimulus and Action Potential

Synaptic cleft
o Gap between nerve and muscle
o Nerve and muscle do not make contact
o Filled with interstitial fluid
Transmission of Nerve Impulse to Muscle

When a nerve impulse reaches the axon terminal of the motor neuron,
1. Calcium channels open, and calcium ions enter the axon terminal
2. Calcium ion entry causes some synaptic vesicles to release acetylcholine
(ACh)
3. ACh diffuses across the synaptic cleft and attaches to receptors on the
sarcolemma of the muscle cell
Transmission of Nerve Impulse to Muscle
4. If enough ACh is released, the sarcolemma becomes temporarily more
permeable to sodium (Na+)
 Sodium rushes into the cell, and potassium leaves the cell
5. Depolarization opens more sodium channels that allow sodium ions to enter
the cell
 Once started, the action potential cannot be stopped, and contraction
occurs
Transmission of Nerve Impulse to Muscle
6. Acetylcholinesterase (AChE) breaks down acetylcholine into acetic acid and
choline
 AChE ends muscle contraction
Transmission of Nerve Impulse to Muscle

Cell returns to its resting state when:
1. Potassium ions diffuse out of the cell
2. Sodium-potassium pump moves sodium and potassium ions back to their
original positions
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Mechanism of Muscle Contraction: The Sliding Filament Theory



Calcium binds to regulatory proteins on thin filaments and exposes myosin-binding
sites, allowing the myosin heads on the thick filaments to attach
The attached heads pivot, sliding the thin filaments toward the center of the
sarcomere, and contraction occurs
ATP provides the energy for the sliding process, which continues as long as ionic
calcium is present
Contraction of Skeletal Muscle




Muscle fiber contraction is “all or none”
Within a skeletal muscle, not all fibers may be stimulated during the same interval
Different combinations of muscle fiber contractions may give differing responses
Graded responses—different degrees of skeletal muscle shortening
Contraction of Skeletal Muscle

Graded responses can be produced by changing:
o The frequency of muscle stimulation
o The number of muscle cells being stimulated at one time
Types of Graded Responses

Twitch
o Single, brief contraction
o Not a normal muscle function
Types of Graded Responses

Summing of contractions
o One contraction is immediately followed by another
o Because stimulations are more frequent, the muscle does not completely
return to a resting state
o The effects are “summed” (added)
Types of Graded Responses

Unfused (incomplete) tetanus
o Some relaxation occurs between contractions, but nerve stimuli arrive at an
even faster rate than during summing of contractions
o Unless the muscle contraction is smooth and sustained, it is said to be in
unfused tetanus
Types of Graded Responses

Fused (complete) tetanus
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o No evidence of relaxation before the following contractions
o Frequency of stimulations does not allow for relaxation between contractions
o The result is a smooth and sustained muscle contraction
Muscle Response to Strong Stimuli



Muscle force depends upon the number of fibers stimulated
Contraction of more fibers results in greater muscle tension
Muscles can continue to contract unless they run out of energy
Energy for Muscle Contraction

ATP
o Immediate source of energy for muscle contraction
o Stored in muscle fibers in small amounts that are quickly used up
o After this initial time, other pathways must be utilized to produce ATP
Energy for Muscle Contraction

Three ways to generate ATP
1. Direct phosphorylation of ADP by creatine phosphate
2. Aerobic respiration
3. Anaerobic glycolysis and lactic acid formation
Energy for Muscle Contraction

Direct phosphorylation of ADP by creatine phosphate (CP)—fastest
o Muscle cells store CP, a high-energy molecule
o After ATP is depleted, ADP remains
o CP transfers a phosphate group to ADP to regenerate ATP
o CP supplies are exhausted in less than 15 seconds
o About 1 ATP is created per CP molecule
Energy for Muscle Contraction

Aerobic respiration
o Glucose is broken down to carbon dioxide and water, releasing energy (about
32 ATP)
o A series of metabolic pathways occurs in the mitochondria
o This is a slower reaction that requires continuous oxygen
o Carbon dioxide and water are produced
Energy for Muscle Contraction

Anaerobic glycolysis and lactic acid formation
o Reaction that breaks down glucose without oxygen
o Glucose is broken down to pyruvic acid to produce about 2 ATP
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
o Pyruvic acid is converted to lactic acid
This reaction is not as efficient, but is fast
o Huge amounts of glucose are needed
o Lactic acid produces muscle fatigue
Muscle Fatigue and Oxygen Deficit


If muscle activity is strenuous and prolonged, muscle fatigue occurs because:
o Ionic imbalances occur
o Lactic acid accumulates in the muscle
o Energy (ATP) supply decreases
After exercise, the oxygen deficit is repaid by rapid, deep breathing
Types of Muscle Contractions


Isotonic contractions
o Myofilaments are able to slide past each other during contractions
o The muscle shortens, and movement occurs
o Example: bending the knee; rotating the arm
Isometric contractions
o Tension in the muscles increases
o The muscle is unable to shorten or produce movement
o Example: pushing against a wall with bent elbows
Muscle Tone

Muscle tone keeps muscles healthy and ready to react
o Result of a staggered series of nerve impulses delivered to different cells within
the muscle
o If the nerve supply is destroyed, the muscle loses tone, becomes paralyzed,
and atrophies
Effect of Exercise on Muscles

Exercise increases muscle size, strength, and endurance
o Aerobic (endurance) exercise (biking, jogging) results in stronger, more flexible
muscles with greater resistance to fatigue
 Makes body metabolism more efficient
 Improves digestion, coordination
o Resistance (isometric) exercise (weight lifting) increases muscle size and
strength
Muscles and Body Movements


Movement is attained as a result of a muscle moving an attached bone
Muscles are attached to at least two points
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1. Origin: attachment to a moveable bone
2. Insertion: attachment to an immovable bone
Types of Body Movements


Flexion
o Decreases the angle of the joint
o Brings two bones closer together
o Typical of bending hinge joints (e.g., knee and elbow) or ball-and-socket joints
(e.g., the hip)
Extension
o Opposite of flexion
o Increases angle between two bones
o Typical of straightening the elbow or knee
o Extension beyond 180° is hyperextension
Types of Body Movements

Rotation
o Movement of a bone around its longitudinal axis
o Common in ball-and-socket joints
o Example: moving the atlas around the dens of axis (i.e., shaking your head
“no”)
Types of Body Movements


Abduction
o Movement of a limb away from the midline
Adduction
o Opposite of abduction
o Movement of a limb toward the midline
Types of Body Movements

Circumduction
o Combination of flexion, extension, abduction, and adduction
o Common in ball-and-socket joints
o Proximal end of bone is stationary, and distal end moves in a circle
Special Movements


Dorsiflexion
o Lifting the foot so that the superior surface approaches the shin (toward the
dorsum)
Plantar flexion
o Depressing the foot (pointing the toes)
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o “Planting” the foot toward the sole
Special Movements


Inversion
o Turning sole of foot medially
Eversion
o Turning sole of foot laterally
Special Movements


Supination
o Forearm rotates laterally so palm faces anteriorly
o Radius and ulna are parallel
Pronation
o Forearm rotates medially so palm faces posteriorly
o Radius and ulna cross each other like an X
Special Movements

Opposition
o Moving the thumb to touch the tips of other fingers on the same hand
Interactions of Skeletal Muscles in the Body


In general, groups of muscles that produce opposite actions lie on opposite sides of a
joint
We will explore examples in Figure 6.14 next
Types of Muscles




Prime mover—muscle with the major responsibility for a certain movement
Antagonist—muscle that opposes or reverses a prime mover
Synergist—muscle that aids a prime mover in a movement and helps prevent rotation
Fixator—stabilizes the origin of a prime mover
Naming Skeletal Muscles


By direction of muscle fibers
o Example: rectus (straight)
By relative size of the muscle
o Example: maximus (largest)
Naming Skeletal Muscles

By location of the muscle
o Example: temporalis (temporal bone)
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
By number of origins
o Example: triceps (three heads)
Naming Skeletal Muscles



By location of the muscle’s origin and insertion
o Example: sterno (on the sternum)
By shape of the muscle
o Example: deltoid (triangular)
By action of the muscle
o Example: flexor and extensor (flexes or extends a bone)
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Functions of the Nervous System
1. Sensory input—gathering information
o To monitor changes occurring inside and outside the body
o Changes = stimuli
2. Integration
o To process and interpret sensory input and decide whether action is needed
Functions of the Nervous System
3. Motor output
o A response to integrated stimuli
o The response activates muscles or glands
Organization of the Nervous System

Nervous system is classified based on:
o Structures (structural classification)
o Activities (functional classification)
Structural Classification of the Nervous System

Central nervous system (CNS)
o Organs
 Brain
 Spinal cord
o Function
 Integration; command center
 Interpret incoming sensory information
 Issues outgoing instructions
Structural Classification of the Nervous System

Peripheral nervous system (PNS)
o Nerves extending from the brain and spinal cord
 Spinal nerves—carry impulses to and from the spinal cord
 Cranial nerves—carry impulses to and from the brain
o Functions
 Serve as communication lines among sensory organs, the brain and
spinal cord, and glands or muscles
Functional Classification of the Peripheral Nervous System

Sensory (afferent) division
o Nerve fibers that carry information to the central nervous system
 Somatic sensory fibers carry information from the skin, skeletal muscles,
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
and joints
 Visceral sensory fibers carry information from visceral organs
Motor (efferent) division
o Nerve fibers that carry impulses away from the central nervous system organs
Functional Classification of the Peripheral Nervous System

Motor (efferent) division (continued)
o Two subdivisions
 Somatic nervous system = voluntary
o Consciously controls skeletal muscles
 Autonomic nervous system = involuntary
o Automatically controls smooth and cardiac muscles and glands
o Further divided into the sympathetic and parasympathetic
nervous systems
Nervous Tissue: Support Cells


Support cells in the CNS are grouped together as neuroglia
General functions
o Support
o Insulate
o Protect neurons
Nervous Tissue: Support Cells

CNS glial cells: astrocytes
o Abundant, star-shaped cells
o Brace neurons
o Form barrier between capillaries and neurons
o Control the chemical environment of
the brain
Nervous Tissue: Support Cells

CNS glial cells: microglia
o Spiderlike phagocytes
o Dispose of debris
Nervous Tissue: Support Cells

CNS glial cells: ependymal cells
o Line cavities of the brain and spinal cord
o Cilia assist with circulation of cerebrospinal fluid
Nervous Tissue: Support Cells
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
CNS glial cells: oligodendrocytes
o Wrap around nerve fibers in the central nervous system
o Produce myelin sheaths
Nervous Tissue: Support Cells

PNS glial cells
o Satellite cells
 Protect neuron cell bodies
o Schwann cells
 Form myelin sheath in the peripheral nervous system
Nervous Tissue: Neurons

Neurons = nerve cells
o Cells specialized to transmit messages
o Major regions of neurons
 Cell body—nucleus and metabolic center of the cell
 Processes—fibers that extend from the cell body
Nervous Tissue: Neurons

Cell body
o Nissl bodies
 Specialized rough endoplasmic reticulum
o Neurofibrils
 Intermediate cytoskeleton
 Maintains cell shape
o Nucleus with large nucleolus
Nervous Tissue: Neurons

Processes outside the cell body
o Dendrites—conduct impulses toward the cell body
 Neurons may have hundreds of dendrites
o Axons—conduct impulses away from the cell body
 Neurons have only one axon arising from the cell body at the axon
hillock
Nervous Tissue: Neurons

Axons
o End in axon terminals
o Axon terminals contain vesicles with neurotransmitters
o Axon terminals are separated from the next neuron by a gap
 Synaptic cleft—gap between adjacent neurons
 Synapse—junction between nerves
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Nervous Tissue: Neurons


Myelin sheath—whitish, fatty material covering axons
o Schwann cells—produce myelin sheaths in jelly roll–like fashion around axons
(PNS)
 Nodes of Ranvier—gaps in myelin sheath along the axon
o Oligodendrocytes—produce myelin sheaths around axons of the CNS
Myelin sheaths speed the nerve impulse transmission
Neuron Cell Body Location


Most neuron cell bodies are found in the central nervous system
o Gray matter—cell bodies and unmyelinated fibers
o Nuclei—clusters of cell bodies within the white matter of the central nervous
system
Ganglia—collections of cell bodies outside the central nervous system
Neuron Cell Body Location




Tracts—bundles of nerve fibers in the CNS
Nerves—bundles of nerve fibers in the PNS
White matter—collections of myelinated fibers (tracts)
Gray matter—collections of mostly unmyelinated fibers and cell bodies
Functional Classification of Neurons

Sensory (afferent) neurons
o Carry impulses from the sensory receptors to the CNS
 Cutaneous sense organs
 Proprioceptors—detect stretch or tension
Functional Classification of Neurons


Motor (efferent) neurons
o Carry impulses from the central nervous system to viscera, muscles, or glands
Interneurons (association neurons)
o Found in neural pathways in the central nervous system
o Connect sensory and motor neurons
Structural Classification of Neurons


Structural classification is based on number of processes extending from the cell body
Multipolar neurons—many extensions from the cell body
o All motor and interneurons are multipolar
o Most common structure
Structural Classification of Neurons
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
Bipolar neurons—one axon and one dendrite
o Located in special sense organs, such as nose and eye
o Rare in adults
Structural Classification of Neurons

Unipolar neurons—have a short single process leaving the cell body
o Sensory neurons found in PNS ganglia
o Conduct impulses both toward and away from the cell body
Functional Properties of Neurons


Irritability
o Ability to respond to a stimulus and convert it to a nerve impulse
Conductivity
o Ability to transmit the impulse to other neurons, muscles, or glands
Nerve Impulses

Resting neuron
o The plasma membrane at rest is polarized
o As long as inside is more negative than outside, the cell stays at rest
o Fewer positive ions are inside the cell than outside the cell
 K+ is the major positive ion inside the cell
 Na+ is the major positive ion outside the cell
Nerve Impulses

Action potential initiation and generation
o A stimulus depolarizes the neuron’s membrane
o The membrane is now permeable to sodium as sodium channels open
o A depolarized membrane allows sodium (Na+) to flow inside the membrane
Nerve Impulses

Action potential initiation and generation
o A stimulus leads to the movement of ions, which initiates an action potential in
the neuron
o A graded potential (localized depolarization) exists where the inside of the
membrane is more positive and the outside is less positive
o If the stimulus is strong enough and sodium influx great enough, local
depolarization activates the neuron to conduct an action potential (nerve
impulse)
Nerve Impulses

Propagation of the action potential
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o If enough sodium enters the cell, the action potential (nerve impulse) starts and
is propagated over the entire axon
o All-or-none response means the nerve impulse either is propagated or is not
o Fibers with myelin sheaths conduct nerve impulses more quickly
Nerve Impulses

Repolarization
o Potassium ions rush out of the neuron after sodium ions rush in, repolarizing
the membrane
o Repolarization involves restoring the inside of the membrane to a negative
charge and the outer surface to a positive charge
o Until repolarization is complete, a neuron cannot conduct another nerve
impulse
Nerve Impulses

Repolarization
o Initial ionic conditions are restored using the sodium-potassium pump
o This pump, using ATP, restores the original configuration
o Three sodium ions are ejected from the cell while two potassium ions are
returned to the cell
Transmission of a Signal at Synapses

When the action potential reaches the axon terminal, the electrical charge opens
calcium channels
Transmission of a Signal at Synapses

Calcium, in turn, causes the tiny vesicles containing the neurotransmitter chemical to
fuse with the axonal membrane
Transmission of a Signal at Synapses

The entry of calcium into the axon terminal causes porelike openings to form,
releasing the transmitter
Transmission of a Signal at Synapses

The neurotransmitter molecules diffuse across the synapse and bind to receptors on
the membrane of the next neuron
Transmission of a Signal at Synapses


If enough neurotransmitter is released, graded potential will be generated
Eventually an action potential (nerve impulse) will occur in the neuron beyond the
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synapse
Transmission of a Signal at Synapses



The electrical changes prompted by neurotransmitter binding are brief
The neurotransmitter is quickly removed from the synapse by either:
o Reuptake
o Enzymatic activity
Transmission of an impulse is electrochemical
o Transmission down neuron is electrical
o Transmission to next neuron is chemical
The Reflex Arc


Reflexes are:
o Rapid
o Predictable
o Involuntary responses to a stimulus
Reflexes occur over neural pathways called reflex arcs
The Reflex Arc


Somatic reflexes
o Reflexes that stimulate the skeletal muscles
o Example: pulling your hand away from a hot object
Autonomic reflexes
o Regulate the activity of smooth muscles, the heart, and glands
o Example: regulation of smooth muscles, heart and blood pressure, glands,
digestive system
The Reflex Arc

Five elements of a reflex:
1. Sensory receptor—reacts to a stimulus
2. Sensory neuron—carries message to the integration center
3. Integration center (CNS)—processes information and directs motor output
4. Motor neuron—carries message to an effector
5. Effector organ—is the muscle or gland to be stimulated
Two-Neuron Reflex Arc

Two-neuron reflex arcs
o Simplest type
o Example: patellar (knee-jerk) reflex
Three-Neuron Reflex Arc
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
Three-neuron reflex arcs
o Consists of five elements: receptor, sensory neuron, interneuron, motor
neuron, and effector
o Example: flexor (withdrawal) reflex
Central Nervous System (CNS)

CNS develops from the embryonic neural tube
o The neural tube becomes the brain and spinal cord
o The opening of the neural tube becomes the ventricles
 Four chambers within the brain
 Filled with cerebrospinal fluid
Regions of the Brain
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Cerebral hemispheres (cerebrum)
Diencephalon
Brain stem
Cerebellum
Regions of the Brain: Cerebrum
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
Cerebral hemispheres are paired (left & right) superior parts of the brain
o Includes more than half of the brain mass
o The surface is made of ridges (gyri) and grooves (sulci)
Three main regions of cerebral hemisphere
1. Cortex (gray matter)
2. White matter
3. Basal nuclei (deep pockets of gray matter)
Regions of the Brain: Cerebrum

Lobes of the cerebrum
o Fissures (deep grooves) divide the cerebrum into lobes
o Surface lobes of the cerebrum
 Frontal lobe
 Parietal lobe
 Occipital lobe
 Temporal lobe
Regions of the Brain: Cerebrum

Specialized areas of the cerebrum
o Primary somatic sensory area
 Receives impulses from the body’s sensory receptors
o Pain, temperature, light touch
 Located in parietal lobe posterior to central sulcus
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
Sensory homunculus is a spatial map
Left side of the primary somatic sensory area receives impulses from
right side (and vice versa)
Regions of the Brain: Cerebrum

Cerebral areas involved in special senses
o Visual area (occipital lobe)
o Auditory area (temporal lobe)
o Olfactory area (temporal lobe)
Regions of the Brain: Cerebrum

Specialized areas of the cerebrum
o Primary motor area
 Sends impulses to skeletal muscles
 Located in frontal lobe
 Motor neurons form corticospinal (pyramidal) tract, which descends to
spinal cord
 Motor homunculus is a spatial map
Regions of the Brain: Cerebrum


Broca’s area
o Involved in our ability to speak
o Usually in left hemisphere
Other specialized areas
o Anterior and posterior association areas
o Speech area
Regions of the Brain: Cerebrum
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
Layers of the cerebrum
o Gray matter—outer layer in the cerebral cortex; composed mostly of neuron
cell bodies
o White matter—fiber tracts deep to the gray matter
 Corpus callosum connects hemispheres
Basal nuclei (ganglia)—islands of gray matter buried within the white matter
Regions of the Brain: Diencephalon
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Sits on top of the brain stem
Enclosed by the cerebral hemispheres
Made of three parts:
1. Thalamus
2. Hypothalamus
3. Epithalamus
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Regions of the Brain: Diencephalon

Thalamus
o Surrounds the third ventricle
o The relay station for sensory impulses
o Transfers impulses to the correct part of the cortex for localization and
interpretation
Regions of the Brain: Diencephalon

Hypothalamus
o Under the thalamus
o Important autonomic nervous system center
 Helps regulate body temperature
 Controls water balance
 Regulates metabolism
o Houses the limbic center for emotions
o Regulates the nearby pituitary gland
o Houses mammillary bodies for olfaction (smell)
Regions of the Brain: Diencephalon

Epithalamus
o Forms the roof of the third ventricle
o Houses the pineal body (an endocrine gland)
o Includes the choroid plexus—forms cerebrospinal fluid
Regions of the Brain: Brain Stem
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
Attaches to the spinal cord
Parts of the brain stem
o Midbrain
o Pons
o Medulla oblongata
Regions of the Brain: Brain Stem

Midbrain
o Composed mostly of tracts of nerve fibers
o Two bulging fiber tracts, cerebral peduncles, convey ascending and
descending impulses
o Four rounded protrusions, corpora quadrigemina, visual and auditory reflex
centers
Regions of the Brain: Brain Stem

Pons
o The bulging center part of the brain stem
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o Mostly composed of fiber tracts
o Includes nuclei involved in the control of breathing
Regions of the Brain: Brain Stem

Medulla oblongata
o The lowest part of the brain stem
o Merges into the spinal cord
o Includes important fiber tracts
o Contains important control centers
 Heart rate control
 Blood pressure regulation
 Breathing
 Swallowing
 Vomiting
Regions of the Brain: Brain Stem

Reticular formation
o Diffuse mass of gray matter along the brain stem
o Involved in motor control of visceral organs
o Reticular activating system (RAS)
 Plays a role in awake/sleep cycles and consciousness
 Filter for incoming sensory information
Regions of the Brain: Cerebellum
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Two hemispheres with convoluted surfaces
Controls balance and equilibrium
Provides precise timing for skeletal muscle activity and coordination of body
movements
Protection of the Central Nervous System
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Scalp and skin
Skull and vertebral column
Meninges
Cerebrospinal fluid (CSF)
Blood-brain barrier
Meninges

Dura mater
o Tough outermost layer
o Double-layered external covering
 Periosteum—attached to inner surface of the skull
 Meningeal layer—outer covering of the brain
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o Folds inward in several areas
 Falx cerebri
 Tentorium cerebelli
Meninges
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
Arachnoid layer
o Middle layer
o Weblike extensions span the subarachnoid space
o Arachnoid villi reabsorb cerebrospinal fluid
Pia mater
o Internal layer
o Clings to the surface of the brain
Cerebrospinal Fluid (CSF)
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Similar to blood plasma composition
Formed by the choroid plexus
o Choroid plexuses–capillaries in the ventricles of the brain
Forms a watery cushion to protect the brain
Circulated in arachnoid space, ventricles, and central canal of the spinal cord
Cerebrospinal Fluid (CSF) Pathway of Flow
1. CSF is produced by the choroid plexus of each ventricle.
2. CSF flows through the ventricles and into the subarachnoid space via the median and
lateral apertures. Some CSF flows through the central canal of the spinal cord.
3. CSF flows through the subarachnoid space.
4. CSF is absorbed into the dural venous sinuses via the arachnoid villi.
Hydrocephalus in a Newborn

Hydrocephalus
o CSF accumulates and exerts pressure on the brain if not allowed to drain
o Possible in an infant because the skull bones have not yet fused
o In adults, this situation results in brain damage
Blood-Brain Barrier



Includes the least permeable capillaries of the body
Excludes many potentially harmful substances
Useless as a barrier against some substances
o Fats and fat-soluble molecules
o Respiratory gases
o Alcohol
o Nicotine
o Anesthesia
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Blood-Brain Barrier
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
Water-soluble items that can travel through barrier:
o Water
o Glucose
o Essential amino acids
Items prevented from passing through:
o Metabolic wastes
o Most drugs
o Nonessential amino acids
o Potassium ions
Traumatic Brain Injuries



Concussion
o Slight brain injury
o No permanent brain damage
Contusion
o Nervous tissue destruction occurs
o Nervous tissue does not regenerate
Cerebral edema
o Swelling from the inflammatory response
o May compress and kill brain tissue
Cerebrovascular Accident (CVA), or Stroke




Results from a ruptured blood vessel supplying a region of the brain
Brain tissue supplied with oxygen from that blood source dies
Loss of some functions or death may result
o Hemiplegia—one-sided paralysis
o Aphasia—damage to speech center in left hemisphere
Transient ischemic attack (TIA)—temporary brain ischemia (restriction of blood flow)
o Warning signs for more serious CVAs
Alzheimer’s Disease




Progressive degenerative brain disease
Mostly seen in the elderly, but may begin in middle age
Structural changes in the brain include abnormal protein deposits and twisted fibers
within neurons
Victims experience memory loss, irritability, confusion, and ultimately, hallucinations
and death
Spinal Cord



Extends from the foramen magnum of the skull to the first or second lumbar vertebra
Provides a two-way conduction pathway to and from the brain
31 pairs of spinal nerves arise from the spinal cord
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
Ends around vertebra L1 or L2
Cauda equina is a collection of spinal nerves at the inferior end
Spinal Cord Anatomy

Internal gray matter is mostly cell bodies
o Dorsal (posterior) horns house interneurons
 Receive information from sensory neurons in the dorsal root
o Anterior (ventral) horns house motor neurons of the somatic (voluntary)
nervous system
 Send information out ventral root
o Gray matter surrounds the central canal, which is filled with cerebrospinal fluid
Spinal Cord Anatomy

Exterior white mater—conduction tracts
o Dorsal, lateral, ventral columns
o Sensory (afferent) tracts conduct impulses toward brain
o Motor (efferent) tracts carry impulses from brain to skeletal muscles
Spinal Cord Anatomy


Meninges cover the spinal cord
Spinal nerves leave at the level of each vertebra
o Dorsal root
 Associated with the dorsal root ganglia—collections of cell bodies
outside the central nervous system
o Ventral root
 Contains axons
Peripheral Nervous System (PNS)



PNS consists of nerves and ganglia outside the central nervous system
Nerve = bundle of neuron fibers
Neuron fibers are bundled by connective tissue
PNS: Structure of a Nerve



Endoneurium surrounds each fiber
Groups of fibers are bound into fascicles by perineurium
Fascicles are bound together by epineurium
PNS: Classification of Nerves


Mixed nerves
o Both sensory and motor fibers
Sensory (afferent) nerves
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
o Carry impulses toward the CNS
Motor (efferent) nerves
o Carry impulses away from the CNS
PNS: Cranial Nerves



12 pairs of nerves that mostly serve the head and neck
Only the pair of vagus nerves extends to thoracic and abdominal cavities
Most are mixed nerves, but three are sensory only:
1. Optic
2. Olfactory
3. Vestibulocochlear
PNS: Cranial Nerves Mnemonic Device
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Oh – Olfactory
Oh – Optic
Oh – Oculomotor
To – Trochlear
Touch – Trigeminal
And – Abducens
Feel – Facial
Very – Vestibulocochlear
Green – Glossopharyngeal
Vegetables – Vagus
A – Accessory
H – Hypoglossal
PNS: Spinal Nerves



There is a pair of spinal nerves at the level of each vertebra, for a total of 31 pairs
Formed by the combination of the ventral and dorsal roots of the spinal cord
Named for the region from which they arise
PNS: Anatomy of Spinal Nerves


Spinal nerves divide soon after leaving the spinal cord
Ramus—branch of a spinal nerve; contains both motor and sensory fibers
o Dorsal rami—serve the skin and muscles of the posterior trunk
o Ventral rami—form a complex of networks (plexus) for the anterior
PNS: Spinal Nerve Plexuses



Plexus–networks of nerves serving motor and sensory needs of the limbs
Form from ventral rami of spinal nerves in the cervical, lumbar, and sacral regions
Four plexuses:
1. Cervical
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2. Brachial
3. Lumbar
4. Sacral
PNS: Autonomic Nervous System



Motor subdivision of the PNS
o Consists only of motor nerves
Also known as the involuntary nervous system
o Regulates activities of cardiac and smooth muscles and glands
Two subdivisions:
1. Sympathetic division
2. Parasympathetic division
PNS: Anatomy of the Parasympathetic Division




Preganglionic neurons originate from the craniosacral regions:
o The cranial nerves III, VII, IX, and X
o S2 through S4 regions of the spinal cord
Because it is the site of preganglionic neuron origination, the parasympathetic division
is also known as the craniosacral division
Terminal ganglia are at the effector organs
Neurotransmitter: acetylcholine
PNS: Anatomy of the Sympathetic Division




Preganglionic neurons originate from T1 through L2
Ganglia are at the sympathetic trunk (near the spinal cord)
Short preganglionic neuron and long postganglionic neuron transmit impulse from
CNS to the effector
Neurotransmitters: norepinephrine and epinephrine (effector organs)
PNS: Autonomic Functioning

Sympathetic—“fight or flight” division
o Response to unusual stimulus
o Takes over to increase activities
o Remember as the “E” division:
 Exercise
 Excitement
 Emergency
 Embarrassment
PNS: Autonomic Functioning

Parasympathetic—“housekeeping” activites
o Conserves energy
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o Maintains daily necessary body functions
o Remember as the “D” division
 Digestion
 Defecation
 Diuresis
Developmental Aspects of the Nervous System
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


The nervous system is formed during the first month of embryonic development
Any maternal infection can have extremely harmful effects
Oxygen deprivation destroys brain cells
The hypothalamus is one of the last areas of the brain to develop
Developmental Aspects of the Nervous System

Severe congenital brain diseases include:
o Cerebral palsy
o Anencephaly
o Hydrocephalus
o Spina bifida
Developmental Aspects of the Nervous System


Premature babies have trouble regulating body temperature because the
hypothalamus is one of the last brain areas to mature prenatally.
Development of motor control indicates the progressive myelination and maturation of
a child’s nervous system.
Developmental Aspects of the Nervous System



Brain growth ends in young adulthood. Neurons die throughout life and are not
replaced; thus, brain mass declines with age.
Healthy aged people maintain nearly optimal intellectual function.
Disease—particularly cardiovascular disease—is the major cause of declining mental
function with age.
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The Senses

Special senses
o Smell
o Taste
o Sight
o Hearing
o Equilibrium
The Eye and Vision
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

70 percent of all sensory receptors are in the eyes
Each eye has over 1 million nerve fibers
Protection for the eye
o Most of the eye is enclosed in a bony orbit
o A cushion of fat surrounds most of the eye
Accessory Structures of the Eye

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

Eyelids and eyelashes
Conjunctiva
Lacrimal apparatus
Extrinsic eye muscles
Accessory Structures of the Eye


Eyelids
o Meet at the medial and lateral commissure (canthus)
Eyelashes
o Tarsal glands produce an oily secretion that lubricates the eye
o Ciliary glands are located between the eyelashes
Accessory Structures of the Eye

Conjunctiva
o Membrane that lines the eyelids
o Connects to the outer surface of the eye
o Secretes mucus to lubricate the eye and keep it moist
Accessory Structures of the Eye

Lacrimal apparatus = lacrimal gland and ducts
o Lacrimal gland—produces lacrimal fluid; situated on lateral aspect of each eye
o Lacrimal canaliculi—drain lacrimal fluid from eyes medially
o Lacrimal sac—provides passage of lacrimal fluid towards nasal cavity
o Nasolacrimal duct—empties lacrimal fluid into the nasal cavity
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Accessory Structures of the Eye

Function of the lacrimal apparatus
o Protects, moistens, and lubricates the eye
o Empties into the nasal cavity
 Lacrimal secretions (tears) contain:
 Dilute salt solution
 Mucus
 Antibodies
 Lysozyme (enzyme that destroys bacteria)
Accessory Structures of the Eye

Extrinsic eye muscles
o Six muscles attach to the outer surface of the eye
o Produce eye movements
Structure of the Eye


Layers forming the wall of the eyeball
o Fibrous layer: outside layer
o Vascular layer: middle layer
o Sensory layer: inside layer
Humors are fluids that fill the interior of the eyeball
Structure of the Eye: The Fibrous Layer


Sclera
o White connective tissue layer
o Seen anteriorly as the “white of the eye”
Cornea
o Transparent, central anterior portion
o Allows for light to pass through
o Repairs itself easily
o The only human tissue that can be transplanted without fear of rejection
Structure of the Eye: Vascular Layer


Choroid is a blood-rich nutritive layer in the posterior of the eye
o Pigment prevents light from scattering
Modified anteriorly into two structures:
1. Ciliary body—smooth muscle attached to lens by ciliary zonule (suspensory
ligament)
2. Iris—regulates amount of light entering eye
 Pigmented layer that gives eye color
 Pupil—rounded opening in the iris
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Structure of the Eye: Sensory Layer

Retina contains two layers
1. Outer pigmented layer absorbs light and prevents it from scattering
2. Inner neural layer
 Contains receptor cells (photoreceptors)
o Rods
o Cones
Structure of the Eye: Sensory Layer



Signals pass from photoreceptors via a two-neuron chain
o Bipolar neurons
o Ganglion cells
Signals leave the retina toward the brain through the optic nerve
Optic disc (blind spot) is where the optic nerve leaves the eyeball
o Cannot see images focused on the optic disc
Structure of the Eye: Sensory Layer

Neurons of the retina and vision
o Rods
 Most are found toward the edges of the retina
 Allow vision in dim light and peripheral vision
 All perception is in gray tones
Structure of the Eye: Sensory Layer


Neurons of the retina and vision
o Cones
 Allow for detailed color vision
 Densest in the center of the retina
 Fovea centralis–lateral to blind spot
o Area of the retina with only cones
o Visual acuity (sharpest vision) is here
No photoreceptor cells are at the optic disc, or blind spot
Structure of the Eye: Sensory Layer

Cone sensitivity
o Three types of cones
o Different cones are sensitive to different wavelengths
o Color blindness is the result of the lack of one cone type
Lens


Biconvex crystal-like structure
Held in place by a suspensory ligament attached to the ciliary body
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Lens


Cataracts result when the lens becomes hard and opaque with age
o Vision becomes hazy and distorted
o Eventually causes blindness in affected eye
Risk factors include:
o Diabetes mellitus
o Frequent exposure to intense sunlight
o Heavy smoking
Two Segments, or Chambers, of the Eye

Lens divides the eye into two chambers:
1. Anterior (aqueous) segment
 Anterior to the lens
 Contains aqueous humor
2. Posterior (vitreous) segment
 Posterior to the lens
 Contains vitreous humor
Anterior Segment

Aqueous humor
o Watery fluid found between lens and cornea
o Similar to blood plasma
o Helps maintain intraocular pressure
o Provides nutrients for the lens and cornea
o Reabsorbed into venous blood through the scleral venous sinus, or canal of
Schlemm
Posterior Segment

Vitreous humor
o Gel-like substance posterior to the lens
o Prevents the eye from collapsing
o Helps maintain intraocular pressure
Ophthalmoscope


Instrument used to illuminate the interior of the eyeball and fundus (posterior wall)
Can detect diabetes, arteriosclerosis, degeneration of the optic nerve and retina
Pathway of Light Through the Eye



Light must be focused to a point on the retina for optimal vision
Light is bent, or refracted, by the cornea, aqueous humor, lens, and vitreous humor
The eye is set for distance vision
(over 20 feet away)
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
Accommodation—the lens must change shape to focus on closer objects (less than
20 feet away)
Pathway of Light Through the Eye


Image formed on the retina is a real image
Real images are:
o Reversed from left to right
o Upside down
o Smaller than the object
Pathway of Light Through the Eye

The pathway of light through the eye:
1. Cornea
2. Aqueous humor
3. Through pupil
4. Aqueous humor
5. Lens
6. Vitreous humor
7. Retina
Visual Fields and Visual Pathways


Optic chiasma
o Location where the optic nerves cross
o Fibers from the medial side of each eye cross over to the opposite side of the
brain
Optic tracts
o Contain fibers from the lateral side of the eye on the same side and the medial
side of the opposite eye
Visual Fields and Visual Pathways

Overlap of the visual fields, and inputs from both eyes to each optic cortex provide for
depth perception
Pathway of Nerve Impulses into Brain

The pathway of nerve impulses from the retina of the eye into the brain:
1. Optic nerve
2. Optic chiasma
3. Optic tract
4. Thalamus
5. Optic radiation
6. Visual cortex in occipital lobe of brain
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Eye Reflexes


Internal muscles are controlled by the autonomic nervous system
o Photopupillary reflex: bright light causes pupils to constrict through action of
radial, circular, and ciliary muscles
o Accommodation pupillary reflex: viewing close objects causes accommodation
Viewing close objects causes convergence (eyes moving medially)
A Closer Look


Emmetropia—eye focuses images correctly on the retina
Myopia (nearsightedness)
o Distant objects appear blurry
o Light from those objects fails to reach the retina and are focused in front of it
o Results from an eyeball that is too long
A Closer Look

Hyperopia (farsightedness)
o Near objects are blurry, whereas distant objects are clear
o Distant objects are focused behind the retina
o Results from an eyeball that is too short or from a “lazy lens”
A Closer Look

Astigmatism
o Images are blurry
o Results from light focusing as lines, not points, on the retina because of
unequal curvatures of the cornea or lens
Homeostatic Imbalances of the Eyes


Night blindness—inhibited rod function that hinders the ability to see at night
Color blindness—genetic conditions that result in the inability to see certain colors
o Due to the lack of one type of cone (partial color blindness)
Homeostatic Imbalances of the Eyes


Glaucoma—can cause blindness due to increasing pressure within the eye
Hemianopia—loss of the same side of the visual field of both eyes; results from
damage to the visual cortex on one side only
The Ear


Houses two senses:
1. Hearing
2. Equilibrium (balance)
Receptors are mechanoreceptors
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
Different organs house receptors for each sense
Anatomy of the Ear

The ear is divided into three areas:
1. External (outer) ear
2. Middle ear (tympanic cavity)
3. Inner ear (bony labyrinth)
The External Ear


Involved in hearing only
Structures of the external ear
o Auricle (pinna)
o External acoustic meatus (auditory canal)
 Narrow chamber in the temporal bone
 Lined with skin and ceruminous (wax) glands
 Ends at the tympanic membrane (eardrum)
The Middle Ear (Tympanic Cavity)



Air-filled cavity within the temporal bone
Involved only in the sense of hearing
Located between tympanic membrane and oval window and round window
The Middle Ear (Tympanic Cavity)

Two tubes are associated with the inner ear:
1. The opening from the auditory canal is covered by the tympanic membrane
2. The pharyngotympanic, or auditory, tube connects the middle ear with the
throat
 Allows for equalizing pressure during yawning or swallowing
 This tube is otherwise collapsed
Bones of the Middle Ear (Tympanic Cavity)


Three bones (ossicles) span the cavity:
1. Malleus (hammer)
2. Incus (anvil)
3. Stapes (stirrup)
Function
o Vibrations from tympanic membrane move the hammer → anvil → stirrup →
oval window of inner ear
Inner Ear or Bony Labyrinth

Includes sense organs for hearing and balance
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


Filled with perilymph
Contains a maze of bony chambers within the temporal bone:
o Cochlea
o Vestibule
o Semicircular canals
Membranous labyrinth is suspended in perilymph and contains endolymph
Organs of Equilibrium


Equilibrium receptors of the inner ear are called the vestibular apparatus
Vestibular apparatus has two functional parts:
1. Static equilibrium
2. Dynamic equilibrium
Static Equilibrium


Maculae—receptors in the vestibule
o Report on the position of the head
o Send information via the vestibular nerve
Anatomy of the maculae
o Hair cells are embedded in the otolithic membrane
o Otoliths (tiny stones) float in a gel around the hair cells
o Movements cause otoliths to bend the hair cells
Dynamic Equilibrium


These receptors respond to angular or rotary movements
Crista ampullaris (in the ampulla of each semicircular canal)—dynamic equilibrium
receptors are located in the semicircular canals
o Tuft of hair cells covered with cupula (gelatinous cap)
o If the head moves, the cupula drags against the endolymph
Dynamic Equilibrium

Action of angular head movements
o The movement of the cupula stimulates the hair cells
o An impulse is sent via the vestibular nerve to the cerebellum
Organs of Hearing

Spiral organ of Corti
o Located within the cochlear duct
o Receptors = hair cells on the basilar membrane
o Gel-like tectorial membrane is capable of bending hair cells
o Cochlear nerve attached to hair cells transmits nerve impulses to auditory
cortex on temporal lobe
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Mechanism of Hearing




Vibrations from sound waves move tectorial membrane
Hair cells are bent by the membrane
An action potential starts in the cochlear nerve
o Impulse travels to the temporal lobe
Continued stimulation can lead to adaptation
Mechanism of Hearing


High-pitched sounds disturb the short, stiff fibers of the basilar membrane
o Receptor cells close to the oval window are stimulated
Low-pitched sounds disturb the long, floppy fibers of the basilar membrane
o Specific hair cells further along the cochlea are affected
Hearing and Equilibrium Deficits

Deafness is any degree of hearing loss
o Conduction deafness results when the transmission of sound vibrations
through the external and middle ears is hindered
o Sensorineural deafness results from damage to the nervous system structures
involved in hearing
o Ménière’s syndrome affects the inner ear and causes progressive deafness
and perhaps vertigo (sensation of spinning)
Chemical Senses: Taste and Smell


Both senses use chemoreceptors
o Stimulated by chemicals in solution
o Taste has four types of receptors
o Smell can differentiate a large range of chemicals
Both senses complement each other and respond to many of the same stimuli
Olfaction—The Sense of Smell



Olfactory receptors are in roof of nasal cavity
o Olfactory receptors cells (neurons) with long cilia known as olfactory hairs
detect chemicals
o Chemicals must be dissolved in mucus for detection by chemoreceptors called
olfactory receptors
Impulses are transmitted via the olfactory filaments to the olfactory nerve
Interpretation of smells is made in the cortex
Taste Buds and the Sense of Taste


Taste buds house the receptor organs
Locations of taste buds
o Most are on the tongue
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o Soft palate
o Cheeks
Taste Buds and the Sense of Taste


The tongue is covered with projections called papillae
o Filiform papillae—sharp with no taste buds
o Fungiform papillae—rounded with taste buds
o Circumvallate papillae—large papillae with taste buds
Taste buds are found on the sides of papillae
Structure of Taste Buds

Gustatory cells are the receptors
o Possess gustatory hairs (long microvilli)
o Hairs are stimulated by chemicals dissolved in saliva
Structure of Taste Buds


Impulses are carried to the gustatory complex by several cranial nerves because taste
buds are found in different areas
o Facial nerve (cranial nerve VII)
o Glossopharyngeal nerve (cranial nerve IX)
o Vagus nerve (cranial nerve X)
Taste buds are replaced frequently by basal cells
Taste Sensations





Sweet receptors respond to sugars, saccharine, some amino acids
Sour receptors respond to H+ ions or acids
Bitter receptors respond to alkaloids
Salty receptors respond to metal ions
Umami receptors respond to the amino acid glutamate or the beefy taste of meat
Developmental Aspects of the Special Senses



Special sense organs are formed early in embryonic development
Maternal infections during the first 5 or 6 weeks of pregnancy may cause visual
abnormalities as well as sensorineural deafness in the developing child
Congenital ear problems usually result from missing pinnas and closed or missing
external acoustic meatuses
Developmental Aspects of the Special Senses


Vision requires the most learning
The infant has poor visual acuity (is farsighted) and lacks color vision and depth
perception at birth
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
The eye continues to grow and mature until age 8 or 9
Developmental Aspects of the Special Senses

Eye problems
o Strabismus—“crossed eyes”; results from unequal pulls by the external eye
muscles in babies
o Ophthalmia neonatorum—conjunctivitis resulting from gonorrhea in the
mother; baby’s eyelids are swollen, and pus is produced
Developmental Aspects of the Special Senses

Problems of aging associated with vision include presbyopia, glaucoma, cataracts,
and arteriosclerosis of the eye’s blood vessels
o Presbyopia—“old vision” results from decreasing lens elasticity that
accompanies aging
Developmental Aspects of the Special Senses



The newborn infant can hear sounds, but initial responses are reflexive
By the toddler stage, the child is listening critically and beginning to imitate sounds as
language development begins
Age-related ear problems:
o Presbycusis—type of sensorineural deafness that may result from otosclerosis
 Otosclerosis—ear ossicles fuse
Developmental Aspects of the Special Senses

Taste and smell are most acute at birth and decrease in sensitivity after age 40 as the
number of olfactory and gustatory receptors decreases
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The Endocrine System



Second controlling system of the body
o Nervous system is the fast-control system
Uses chemical messengers (hormones) that are released into the blood
Hormones control several major processes:
o Reproduction
o Growth and development
o Mobilization of body defenses
o Maintenance of much of homeostasis
o Regulation of metabolism
Hormone Overview





Hormones are produced by specialized cells
Cells secrete hormones into extracellular fluids
Blood transfers hormones to target sites
These hormones regulate the activity of other cells
Endocrinology is the scientific study of hormones and endocrine organs
The Chemistry of Hormones

Hormones are classified chemically as
o Amino acid–based, which includes:
 Proteins
 Peptides
 Amines
o Steroids—made from cholesterol
o Prostaglandins—made from highly active lipids that act as local hormones
Hormone Action



Hormones affect only certain tissues or organs (target cells or target organs)
Target cells must have specific protein receptors
Hormone binding alters cellular activity
Hormone Action
Hormones arouse cells, or alter cellular activity. Typically, one or more of the following
occurs:
1. Changes in plasma membrane permeability or electrical state
2. Synthesis of proteins, such as enzymes
3. Activation or inactivation of enzymes
4. Stimulation of mitosis
5. Promotion of secretory activity
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The Chemistry of Hormones

Hormones act by two mechanisms:
1. Direct gene activation
2. Second-messenger system
Direct Gene Activation (Steroid Hormone Action)
1.
2.
3.
4.
5.
6.
Steroid hormones diffuse through the plasma membrane of target cells
Steroid hormones enter the nucleus
Steroid hormones bind to a specific protein within the nucleus
Hormone-receptor complex binds to specific sites on the cell’s DNA
Certain genes are activated that result in…
Synthesis of new proteins
Second-Messenger System (Nonsteroid Hormone Action)
1. Hormone (first messenger) binds to a membrane receptor
2. Activated receptor sets off a series of reactions that activates an enzyme
3. Enzyme catalyzes a reaction that produces a second-messenger molecule (such as
cyclic AMP, or cAMP)
4. Oversees additional intracellular changes to promote a specific response in the target
cell
Control of Hormone Release



Hormone levels in the blood are maintained mostly by negative feedback
A stimulus or low hormone levels in the blood triggers the release of more hormone
Hormone release stops once an appropriate level in the blood is reached
Endocrine Gland Stimuli

The stimuli that activate endocrine glands fall into three major categories:
1. Hormonal
2. Humoral
3. Neural
Hormonal Stimuli of Endocrine Glands



Most common stimulus
Endocrine organs are activated by other hormones
Example:
o Anterior pituitary hormones travel to target glands, such as the thyroid gland, to
prompt the release of a particular hormone, such as thyroid hormone
Humoral Stimuli of Endocrine Glands

Changing blood levels of certain ions and nutrients stimulate hormone release
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
o Humoral indicates various body fluids, such as blood and bile
Examples:
o Parathyroid hormone and calcitonin are produced in response to changing
levels of blood calcium levels
o Insulin is produced in response to changing levels of blood glucose levels
Neural Stimuli of Endocrine Glands



Nerve impulses stimulate hormone release
Most are under the control of the sympathetic nervous system
Examples:
o The release of norepinephrine and epinephrine by the adrenal medulla
Major Endocrine Organs









Pituitary gland
Thyroid gland
Parathyroid glands
Adrenal glands
Pineal gland
Thymus gland
Pancreas
Gonads (ovaries and testes)
Hypothalamus
Major Endocrine Organs




Some glands are purely endocrine
o Anterior pituitary, thyroid, adrenals, parathyroids
Endocrine glands are ductless glands
Hormones are released directly into blood or lymph
Other glands are mixed glands, with both endocrine and exocrine functions
(pancreas, gonads)
Pituitary Gland and Hypothalamus

Pituitary gland is the size of a pea
o Hangs by a stalk from the hypothalamus in the brain
o Protected by the sphenoid bone
o Has two functional lobes
 Anterior pituitary—glandular tissue
 Posterior pituitary—nervous tissue
o Often called the “master endocrine gland”
Pituitary Gland and Hypothalamus

Hypothalamus produces releasing and inhibiting hormones
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
o These hormones are released into portal circulation, which connects
hypothalamus to anterior pituitary
Hypothalamus also makes two hormones: oxytocin and antidiuretic hormone
o Carried to posterior pituitary via neurosecretory cells for storage
Posterior Pituitary and Hypothalamic Hormones

Oxytocin
o Stimulates contractions of the uterus during labor, sexual relations, and
breastfeeding
o Causes milk ejection (let-down reflex) in a breastfeeding woman
Posterior Pituitary and Hypothalamic Hormones

Antidiuretic hormone (ADH)
o Inhibits urine production (diuresis) by promoting water reabsorption by the
kidneys
o In large amounts, causes vasoconstriction of arterioles, leading to increased
blood pressure (the reason why ADH is known as vasopressin)
o Alcohol inhibits ADH secretion
o Diabetes insipidus results from ADH hyposecretion
Hormones of the Anterior Pituitary

Six anterior pituitary hormones
o Two affect nonendocrine targets:
1. Growth hormone
2. Prolactin
Hormones of the Anterior Pituitary

Four stimulate other endocrine glands to release hormones (tropic hormones):
1. Thyroid-stimulating hormone (thyrotropic hormone)
2. Adrenocorticotropic hormone
3. Follicle-stimulating hormone
4. Luteinizing hormone
Hormones of the Anterior Pituitary

Characteristics of all anterior pituitary hormones
o Protein (or peptides) structure
o Act through second-messenger systems
o Regulated by hormonal stimuli
o Regulated mostly by negative feedback
Hormones of the Anterior Pituitary
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
Growth hormone (GH)
o General metabolic hormone
o Major effects are directed to growth of skeletal muscles and long bones
o Plays a role in determining final body size
o Causes amino acids to be built into proteins
o Causes fats to be broken down for a source of energy
Hormones of the Anterior Pituitary

Growth hormone (GH) disorders
o Pituitary dwarfism results from hyposecretion of GH during childhood
o Gigantism results from hypersecretion of GH during childhood
o Acromegaly results from hypersecretion of GH during adulthood
Hormones of the Anterior Pituitary


Prolactin (PRL)
o Stimulates and maintains milk production following childbirth
o Function in males is unknown
Adrenocorticotropic hormone (ACTH)
o Regulates endocrine activity of the adrenal cortex
Hormones of the Anterior Pituitary

Thyrotropic hormone (TH), also called thyroid-stimulating hormone (TSH)
o Influences growth and activity of the thyroid gland
Hormones of the Anterior Pituitary

Gonadotropic hormones
o Regulate hormonal activity of the gonads
 Follicle-stimulating hormone (FSH)
o Stimulates follicle development in ovaries
o Stimulates sperm development in testes
 Luteinizing hormone (LH)
o Triggers ovulation of an egg in females
o Stimulates testosterone production in males
Thyroid Gland



Found at the base of the throat
Consists of two lobes and a connecting isthmus
Produces two hormones:
1. Thyroid hormone
2. Calcitonin
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Thyroid Gland

Thyroid hormone
o Major metabolic hormone
o Controls rate of oxidation of glucose to supply body heat and chemical energy
o Needed for tissue growth and development
o Composed of two active iodine-containing hormones
 Thyroxine (T4)—secreted by thyroid follicles
 Triiodothyronine (T3)—conversion of T4 at target tissues
Thyroid Gland

Thyroid hormone disorders
o Goiters
 Thyroid gland enlarges because of lack of iodine
 Salt is iodized to prevent goiters
o Cretinism
 Caused by hyposecretion of thyroxine
 Results in dwarfism during childhood
Thyroid Gland

Thyroid hormone disorders (continued)
o Myxedema
 Caused by hypothyroidism in adults
 Results in physical and mental sluggishness
o Graves’ disease
 Caused by hyperthyroidism
 Results in increased metabolism, heat intolerance, rapid heartbeat,
weight loss, and exophthalmos
Thyroid Gland

Calcitonin
o Decreases blood calcium levels by causing calcium deposition on bone
o Antagonistic to parathyroid hormone
o Produced by parafollicular cells found between the follicles
Parathyroid Glands


Tiny masses on the posterior of the thyroid
Secrete parathyroid hormone (PTH)
o Stimulates osteoclasts to remove calcium from bone
o Hypercalcemic hormone (increases blood calcium levels)
o Stimulates the kidneys and intestine to absorb more calcium
Adrenal Glands
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

Sit on top of the kidneys
Two regions:
1. Adrenal cortex—outer glandular region has three layers that produce
corticosteroids
 Mineralocorticoids are secreted by outermost layer
 Glucocorticoids are secreted by middle layer
 Sex hormones are secreted by innermost layer
2. Adrenal medulla—inner neural tissue region
Hormones of the Adrenal Cortex

Mineralocorticoids (mainly aldosterone)
o Produced in outer adrenal cortex
o Regulate mineral content in blood, particularly sodium and potassium ions
o Regulate water and electrolyte balance
o Target organ is the kidney
Hormones of the Adrenal Cortex


Release of aldosterone is stimulated by:
o Humoral factors (fewer sodium ions or too many potassium ions in the blood)
o Hormonal stimulation (ACTH)
o Renin and angiotensin II in response to a drop in blood pressure
Aldosterone production is inhibited by atrial natriuretic peptide (ANP), a hormone
produced by the heart when blood pressure is too high
Hormones of the Adrenal Cortex

Glucocorticoids (including cortisone and cortisol)
o Produced by middle layer of adrenal cortex
o Promote normal cell metabolism
o Help resist long-term stressors by increasing blood glucose levels
(hyperglycemic hormone)
o Anti-inflammatory properties
o Released in response to increased blood levels of ACTH
Hormones of the Adrenal Cortex

Sex hormones
o Produced in the inner layer of the adrenal cortex
o Small amounts are made throughout life
o Mostly androgens (male sex hormones) are made, but some estrogens (female
sex hormones) are also formed
Adrenal Glands

Adrenal cortex disorders
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o Addison’s disease
 Results from hyposecretion of all adrenal cortex hormones
 Bronze skin tone, muscle weakness, burnout, susceptibility to infection
o Hyperaldosteronism
 May result from an ACTH-releasing tumor
 Excess water and sodium are retained, leading to high blood pressure
and edema
Adrenal Glands

Adrenal cortex disorders (continued)
o Cushing’s syndrome
 Results from a tumor in the middle cortical area of the adrenal cortex
 “Moon face,” “buffalo hump” on the upper back, high blood pressure,
hyperglycemia, weakening of bones, depression
o Masculinization
 Results from hypersecretion of sex hormones
 Beard and male distribution of hair growth
Hormones of the Adrenal Medulla


Produces two similar hormones: (catecholamines)
1. Epinephrine (adrenaline)
2. Norepinephrine (noradrenaline)
These hormones prepare the body to deal with short-term stress (“fight or flight”) by:
o Increasing heart rate, blood pressure, blood glucose levels
o Dilating small passageways of lungs
Pancreatic Islets


Pancreas
o Located in the abdomen, close to stomach
o Mixed gland, with both endocrine and exocrine functions
The pancreatic islets produce hormones
o Insulin—produced by beta cells
o Glucagon—produced by alpha cells
o These hormones are antagonists that maintain blood sugar homeostasis
Pancreatic Islets


Insulin
o Released when blood glucose levels are high
o Increases the rate of glucose uptake and metabolism by body cells
Glucagon
o Released when blood glucose levels are low
o Stimulates the liver to release glucose to blood, thus increasing blood glucose
levels
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Homeostatic Imbalance

Diabetes mellitus
o Occurs in the absence of insulin
o Blood sugar levels increase dramatically
o Blood glucose is lost in the urine; water follows
o Three cardinal signs:
1. Polyuria
2. Polydipsia
3. Polyphagia
Pineal Gland


Located posterior to the third ventricle of the brain
Secretes melatonin
o Helps establish the body’s sleep/wake cycles as well as biological rhythms
o Believed to coordinate the hormones of fertility in humans
Thymus Gland



Located posterior to the sternum
Largest in infants and children
Produces thymosin
o Matures some types of white blood cells
o Important in developing the immune system
Gonads


Ovaries
o Produce eggs
o Produce two groups of steroid hormones:
1. Estrogens
2. Progesterone
Testes
o Produce sperm
o Produce androgens, such as testosterone
Hormones of the Ovaries


Estrogens
o Stimulate the development of secondary female characteristics
o Mature female reproductive organs
With progesterone, estrogens also
o Promote breast development
o Regulate menstrual cycle
Hormones of the Ovaries
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
Progesterone
o Acts with estrogen to bring about the menstrual cycle
o Helps in the implantation of an embryo in the uterus
o Helps prepare breasts for lactation
Hormones of the Testes


Produce several androgens
Testosterone is the most important androgen
o Responsible for adult male secondary sex characteristics
o Promotes growth and maturation of male reproductive system
o Required for sperm cell production
Other Hormone-Producing Tissues and Organs





Parts of the small intestine
Parts of the stomach
Kidneys
Heart
Many other areas have scattered endocrine cells
Placenta



Produces hormones that maintain pregnancy
Some hormones play a part in the delivery of the baby
Produces human chorionic gonadotropin (hCG) in addition to estrogen, progesterone,
and other hormones
Developmental Aspects of the Endocrine System


In the absence of disease, efficiency of the endocrine system remains high until old
age
Decreasing function of female ovaries at menopause leads to such symptoms as
osteoporosis, increased chance of heart disease, and possible mood changes
Developmental Aspects of the Endocrine System

Efficiency of all endocrine glands gradually decreases with aging, which leads to a
generalized increase in incidence of:
o Diabetes mellitus
o Immune system depression
o Lower metabolic rate
o Cancer rates in some areas
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Blood

Blood transports everything that must be carried from one place to another, such as:
o Nutrients
o Wastes
o Hormones
o Body heat
Blood



The only fluid tissue in the human body
Classified as a connective tissue
Components of blood
o Living cells
 Formed elements
o Nonliving matrix
 Plasma
Blood

If blood is centrifuged:
o Erythrocytes sink to the bottom (45 percent of blood, a percentage known as
the hematocrit)
o Buffy coat contains leukocytes and platelets (less than 1 percent of blood)
 Buffy coat is a thin, whitish layer between the erythrocytes and plasma
o Plasma rises to the top (55 percent of blood)
Physical Characteristics of Blood





Color range
o Oxygen-rich blood is scarlet red
o Oxygen-poor blood is dull red
pH must remain between 7.35 and 7.45
Blood temperature is slightly higher than body temperature, at 100.4°F
In a healthy man, blood volume is about 5–6 liters, or about 6 quarts
Blood makes up 8 percent of body weight
Blood Plasma


Composed of approximately 90 percent water
Includes many dissolved substances:
o Nutrients
o Salts (electrolytes)
o Respiratory gases
o Hormones
o Plasma proteins
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o Waste products
Blood Plasma

Plasma proteins
o Most abundant solutes in plasma
o Most plasma proteins are made by liver
o Various plasma proteins include
 Albumin—regulates osmotic pressure
 Clotting proteins—help to stem blood loss when a blood vessel is injured
 Antibodies—help protect the body from pathogens
Blood Plasma



Acidosis
o Blood pH becomes too acidic
Alkalosis
o Blood pH becomes too basic
In each scenario, the respiratory system and kidneys help restore blood pH to normal
Formed Elements



Erythrocytes
o Red blood cells (RBCs)
Leukocytes
o White blood cells (WBCs)
Platelets
o Cell fragments
Formed Elements

Erythrocytes (red blood cells, or RBCs)
o Main function is to carry oxygen
o Anatomy of circulating erythrocytes
 Biconcave disks
 Essentially bags of hemoglobin
 Anucleate (no nucleus)
 Contain very few organelles
o 5 million RBCs per cubic millimeter of blood is the normal count
Formed Elements

Hemoglobin
o Iron-containing protein
o Binds strongly, but reversibly, to oxygen
o Each hemoglobin molecule has four oxygen binding sites
o Each erythrocyte has 250 million hemoglobin molecules
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o Normal blood contains 12–18 g of hemoglobin per 100 mL of blood
Formed Elements

Homeostatic imbalance of RBCs
o Anemia is a decrease in the oxygen-carrying ability of the blood
o Sickle cell anemia (SCA) results from abnormally shaped hemoglobin
o Polycythemia is an excessive or abnormal increase in the number of RBCs
Formed Elements

Polcythemia
o Disorder resulting from excessive or abnormal increase of RBCs
 May be caused by bone marrow cancer (polycythemia vera)
 May be a response to life at higher altitudes (secondary polycythemia)
o Increase in RBCs slows blood flow and increases blood viscosity
Formed Elements

Leukocytes (white blood cells, or WBCs)
o Crucial in body’s defense against disease
o Complete cells, with nucleus and organelles
o Able to move into and out of blood vessels (diapedesis)
o Move by amoeboid motion
o Respond to chemicals released by damaged tissues (known as positive
chemotaxis)
o 4,800 to 10,800 WBCs per cubic millimeter of blood
Formed Elements

Abnormal numbers of leukocytes
o Leukocytosis

WBC count above 11,000 cells/mm3
 Generally indicates an infection
o Leukopenia
 Abnormally low leukocyte level
 Commonly caused by certain drugs, such as corticosteroids and
anticancer agents
Formed Elements

Abnormal numbers of leukocytes (continued)
o Leukemia
 Bone marrow becomes cancerous; turns out excess WBCs
Formed Elements
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
Types of leukocytes:
o Granulocytes
 Granules in their cytoplasm can be stained
 Possess lobed nuclei
 Include neutrophils, eosinophils, and basophils
o Agranulocytes
 Lack visible cytoplasmic granules
 Nuclei are spherical, oval, or kidney-shaped
 Include lymphocytes and monocytes
Formed Elements


List of the WBCs, from most to least abundant
o Neutrophils
o Lymphocytes
o Monocytes
o Eosinophils
o Basophils
Easy way to remember this list
o Never
o Let
o Monkeys
o Eat
o Bananas
Formed Elements

Types of granulocytes:
o Neutrophils
 Cytoplasm stains pale pink and contains fine granules
 Deep purple nucleus contains three to seven lobes
 Function as phagocytes at active sites of infection
 Numbers increase during infection
 3,000–7,000 neutrophils in a cubic millimeter of blood (40–70 percent of
WBCs)
Formed Elements

Types of granulocytes (continued):
o Eosinophils
 Red, coarse cytoplasmic granules
 Figure-8 or bilobed nucleus stains blue-red
 Function to kill parasitic worms and play a role in allergy attacks
 100–400 eosinophils in a cubic millimeter of blood
(1–4 percent of WBCs)
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Formed Elements

Types of granulocytes (continued):
o Basophils
 Sparse but large blue-purple granules
 U- or S-shaped nucleus stains dark blue
 Release histamine (vasodilator) at sites of inflammation
 Contain heparin (anticoagulant)
 20–50 basophils in a cubic millimeter of blood
(0–1 percent of WBCs)
Formed Elements

Types of agranulocytes:
o Lymphocytes
 Cytoplasm is pale blue
 Dark purple-blue nucleus
 Functions as part of the immune response
o B lymphocytes produce antibodies
o T lymphocytes are involved in graft rejection, fighting tumors and
viruses
 1,500–3,000 lymphocytes in a cubic millimeter of blood (20–45 percent
of WBCs)
Formed Elements

Types of agranulocytes (continued):
o Monocytes
 Largest of the white blood cells
 Gray-blue cytoplasm
 Dark blue-purple nucleus is often kidney-shaped
 Function as macrophages
 Important in fighting chronic infection
 100–700 monocytes per cubic millimeter of blood
(4–8 percent of WBCs)
Formed Elements

Platelets
o Derived from ruptured multinucleate cells (megakaryocytes)
o Needed for the clotting process
o Platelet count ranges from 150,000 to 400,000 per cubic millimeter of blood
 300,000 is considered a normal number of platelets per cubic millimeter
of blood
Hematopoiesis

Hematopoiesis is the process of blood cell formation
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


Occurs in red bone marrow
All blood cells are derived from a common stem cell (hemocytoblast)
Hemocytoblast differentiation
o Lymphoid stem cell produces lymphocytes
o Myeloid stem cell produces all other formed elements
Formation of Red Blood Cells




Since RBCs are anucleate, they are unable to divide, grow, or synthesize proteins
RBCs wear out in 100 to 120 days
When worn out, RBCs are eliminated by phagocytes in the spleen or liver
Lost cells are replaced by division of hemocytoblasts in the red bone marrow
Control of Erythrocyte Production



Rate of RBC production is controlled by a hormone called erythropoietin
Kidneys produce most erythropoietin as a response to reduced oxygen levels in the
blood
Homeostasis is maintained by negative feedback from blood oxygen levels
Formation of White Blood Cells and Platelets

Controlled by hormones
o Colony stimulating factors (CSFs) and interleukins prompt bone marrow to
generate leukocytes
o Thrombopoietin stimulates production of platelets
Hemostasis


Stoppage of bleeding resulting from a break in a blood vessel
Hemostasis involves three phases:
1. Vascular spasms
2. Platelet plug formation
3. Coagulation (blood clotting)
Hemostasis

Vascular spasms
o Vasoconstriction causes blood vessel to spasm
o Spasms narrow the blood vessel, decreasing blood loss
Hemostasis

Platelet plug formation
o Collagen fibers are exposed by a break in a blood vessel
o Platelets become “sticky” and cling to fibers
o Anchored platelets release chemicals to attract more platelets
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o Platelets pile up to form a platelet plug (white thrombus)
Hemostasis

Coagulation
o Injured tissues release tissue factor (TF)
o PF3 (a phospholipid) interacts with TF, blood protein clotting factors, and
calcium ions to trigger a clotting cascade
o Prothrombin activator converts prothrombin to thrombin (an enzyme)
Hemostasis

Coagulation (continued)
o Thrombin joins fibrinogen proteins into hairlike molecules of insoluble fibrin
o Fibrin forms a meshwork (the basis for a clot)
o Within the hour, serum is squeezed from the clot as it retracts
 Serum is plasma minus clotting proteins
Hemostasis



Blood usually clots within 3 to 6 minutes
The clot remains as endothelium regenerates
The clot is broken down after tissue repair
Undesirable Clotting


Thrombus
o A clot in an unbroken blood vessel
o Can be deadly in areas such as the heart
Embolus
o A thrombus that breaks away and floats freely in the bloodstream
o Can later clog vessels in critical areas such as the brain
Bleeding Disorders


Thrombocytopenia
o Platelet deficiency
o Even normal movements can cause bleeding from small blood vessels that
require platelets for clotting
o Evidenced by petechiae (small purplish blotches on the skin)
Hemophilia
o Hereditary bleeding disorder
o Normal clotting factors are missing
Blood Groups and Transfusions

Large losses of blood have serious consequences
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
o Loss of 15 to 30 percent causes weakness
o Loss of over 30 percent causes shock, which can be fatal
Blood transfusions are given for substantial blood loss, to treat severe anemia, or for
thrombocytopenia
Human Blood Groups




Blood contains genetically determined proteins
Antigens are substances that the body recognizes as foreign and that the immune
system may attack
Antibodies are the “recognizers”
Blood is “typed” by using antibodies that will cause blood with certain proteins to clump
(agglutination) and lyse
Human Blood Groups


There are over 30 common red blood cell antigens
The most vigorous transfusion reactions are caused by ABO and Rh blood group
antigens
ABO Blood Groups


Based on the presence or absence of two antigens:
1. Type A
2. Type B
The lack of these antigens is called type O
ABO Blood Groups




The presence of both antigens A and B is called type AB
The presence of antigen A is called type A
The presence of antigen B is called type B
The lack of both antigens A and B is called type O
ABO Blood Groups




Blood type AB can receive A, B, AB, and O blood
o Universal recipient
Blood type B can receive B and O blood
Blood type A can receive A and O blood
Blood type O can receive O blood
o Universal donor
Rh Blood Groups

Named because of the presence or absence of one of eight Rh antigens
(agglutinogen D) that was originally defined in Rhesus monkeys
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


Most Americans are Rh+ (Rh-positive)
Problems can occur in mixing Rh+ blood into a body with Rh– (Rh-negative) blood
Hemolysis does not occur with first transfusion, because it takes time to make
antibodies
Second, and subsequent, transfusions involve antibodies attacking donor’s Rh+ RBCs
Rh Dangers During Pregnancy


Danger occurs only when the mother is Rh– and the father is Rh+, and the child inherits
the Rh+ factor
RhoGAM shot can prevent buildup of anti-Rh+ antibodies in mother’s blood
Rh Dangers During Pregnancy

The mismatch of an Rh– mother carrying an Rh+ baby can cause problems for the
unborn child
o The first pregnancy usually proceeds without problems
o The immune system is sensitized after the first pregnancy
o In a second pregnancy, the mother’s immune system produces antibodies to
attack the Rh+ blood (hemolytic disease of the newborn)
Blood Typing




Blood samples are mixed with anti-A and
anti-B serum
Agglutination or the lack of agglutination leads to identification of blood type
Typing for ABO and Rh factors is done in the same manner
Cross matching—testing for agglutination of donor RBCs by the recipient’s serum,
and vice versa
Developmental Aspects of Blood

Sites of blood cell formation
o The fetal liver and spleen are early sites of blood cell formation
o Bone marrow takes over hematopoiesis by the seventh month
Developmental Aspects of Blood




Congenital blood defects include various types of hemolytic anemias and hemophilia
Incompatibility between maternal and fetal blood can result in fetal cyanosis, resulting
from destruction of fetal blood cells
Fetal hemoglobin differs from hemoglobin produced after birth
Physiologic jaundice occurs in infants when the liver cannot rid the body of
hemoglobin breakdown products fast enough
Developmental Aspects of Blood
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
Leukemias are most common in the very young and very old
o Older adults are also at risk for anemia and clotting disorders
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The Cardiovascular System


A closed system of the heart and blood vessels
o The heart pumps blood
o Blood vessels allow blood to circulate to all parts of the body
Functions of the cardiovascular system:
o Deliver oxygen and nutrients to cells and tissues
o Remove carbon dioxide and other waste products from cells and tissues
The Heart



Location
o Thorax, between the lungs in the inferior mediastinum
Orientation
o Pointed apex directed toward left hip
o Base points toward right shoulder
About the size of a human fist
Coverings and Walls of the Heart

Pericardium—a double-walled sac
o Fibrous pericardium is loose and superficial
o Serous membrane is deep to the fibrous pericardium and composed of two
layers:
1. Parietal pericardium: outside layer that lines the inner surface of the
fibrous pericardium
2. Visceral pericardium: next to heart; also known as the epicardium
o Serous fluid fills the space between the layers of pericardium
Coverings and Walls of the Heart

Three layers of the heart wall:
1. Epicardium
 Outside layer
 This layer is the visceral pericardium
 Connective tissue layer
2. Myocardium
 Middle layer
 Mostly cardiac muscle
3. Endocardium
 Inner layer known as endothelium
Chambers and Associated Great Vessels


Right and left side act as separate pumps
Four chambers:
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o Atria (right and left)
 Receiving chambers
o Ventricles (right and left)
 Discharging chambers
Chambers and Associated Great Vessels


Interventricular septum
o Separates the two ventricles
Interatrial septum
o Separates the two atria
Chambers and Associated Great Vessels

Pulmonary circulation
o Blood flows from the right side of the heart to the lungs and back to the left side
of the heart
 Blood is pumped out of right side through the pulmonary trunk, which
splits into pulmonary arteries and takes oxygen-poor blood to lungs
 Oxygen-rich blood returns to the heart from the lungs via pulmonary
veins
Chambers and Associated Great Vessels

Systemic circulation
o Blood flows from the left side of the heart through body tissues, and back to the
right side of the heart
 Blood returned to the left side of the heart is pumped out into the aorta
 Oxygen-poor blood circulates to systemic tissues, and returns to the
right atrium via systemic veins, which empty blood into the superior and
inferior venae cavae
Heart Valves


Allow blood to flow in only one direction, to prevent backflow
Four valves
o Atrioventricular (AV) valves—between atria and ventricles
 Bicuspid (mitral) valve (left side of heart)
 Tricuspid valve (right side of heart)
o Semilunar valves—between ventricle and artery
 Pulmonary semilunar valve
 Aortic semilunar valve
Heart Valves

AV valves
o Anchored in place by chordae tendineae (“heart strings”)
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
o Open during heart relaxation and closed during ventricular contraction
Semilunar valves
o Closed during heart relaxation but open during ventricular contraction
These valves open and close in response to pressure changes in the heart
Cardiac Circulation



Blood in the heart chambers does not nourish the myocardium
The heart has its own nourishing circulatory system consisting of:
o Coronary arteries—branch from the aorta to supply the heart muscle with
oxygenated blood
o Cardiac veins—drain the myocardium of blood
o Coronary sinus—a large vein on the posterior of the heart, receives blood from
cardiac veins
Blood empties into the right atrium via the coronary sinus
Blood Flow Through the Heart




Superior and inferior venae cavae dump blood into the right atrium
From right atrium, through the tricuspid valve, blood travels to the right ventricle
From the right ventricle, blood leaves the heart as it passes through the pulmonary
semilunar valve into the pulmonary trunk
Pulmonary trunk splits into right and left pulmonary arteries, which carry blood to the
lungs
Blood Flow Through the Heart




In the lungs, blood picks up oxygen and drops off carbon dioxide
Oxygen-rich blood returns to the heart through the four pulmonary veins
Blood enters the left atrium and travels through the bicuspid valve into the left ventricle
From the left ventricle, blood leaves the heart via the aortic semilunar valve and aorta
Intrinsic Conduction System of the Heart: Setting the Basic Rhythm


Cardiac muscle is able to initiate its own contraction in a regular way, but its rate is
influenced by both intrinsic and extrinsic factors
The intrinsic conduction (nodal) system increases the rate of heart contraction and
ensures that the heart beats as a unit
Intrinsic Conduction System of the Heart: Setting the Basic Rhythm





Sinoatrial (SA) node is the heart’s pacemaker
Atrioventricular (AV) node is at the junction of the atria and ventricles
Atrioventricular (AV) bundle (bundle of His) is in the interventricular septum
Bundle branches are in the interventricular septum
Purkinje fibers spread within the ventricle wall muscles
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Heart Contractions




Intrinsic conduction system enforces 75 beats per minute
Contraction is initiated by the sinoatrial node
(SA node)
Sequential stimulation occurs at other autorhythmic cells
Force cardiac muscle depolarization in one direction—from atria to ventricles
Heart Contractions



Once SA node starts the heartbeat
o Impulse spreads to the AV node
o Then the atria contract
At the AV node, the impulse passes through the AV bundle, bundle branches, and
Purkinje fibers
Blood is ejected from the ventricles to the aorta and pulmonary trunk as the ventricles
contract
Heart Contractions

Homeostatic imbalance
o Heart block—damaged AV node releases the ventricles from control of the SA
node; result is in a slower heart rate as ventricles contract at their own rate
o Ischemia—lack of adequate oxygen supply to heart muscle
o Fibrillation—a rapid, uncoordinated shuddering of the heart muscle
Heart Contractions

Homeostatic imbalance (continued)
o Tachycardia—rapid heart rate over 100 beats per minute
o Bradycardia—slow heart rate less than 60 beats per minutes
Cardiac Cycle & Heart Sounds



Cardiac cycle refers to one complete heartbeat
o Systole = contraction
o Diastole = relaxation
Heart beats approximately 75 times per minute
Cardiac cycle length is normally 0.8 second
Cardiac Cycle & Heart Sounds

Mid-to-late diastole
o Pressure in heart is low
o Blood flows passively into the atria and into ventricles
o Semilunar valves are closed
o Atrioventricular valves are open
o Atria contract and force blood into ventricles
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Cardiac Cycle & Heart Sounds

Ventricular systole
o Blood pressure rises as ventricles prepare to contract
o Atrioventricular valves close causing first heart sound, “lub”
o Semilunar valves open as blood pushes against them
o Blood travels out of the ventricles through pulmonary trunk and aorta
o Atria are relaxed and filling with blood
Cardiac Cycle & Heart Sounds

Early diastole
o At the end of systole, all four valves are briefly closed at the same time
 Second heart sound is heard as semilunar valves close, causing “dup”
sound
 Closure prevents blood backflow into ventricles
o Atria finish refilling as pressure in heart drops
o Ventricular pressure is low
o Atrioventricular valves open
Homeostatic Imbalance

Faulty valves reduce the efficiency of the heart as a pump and result in abnormal heart
sounds (murmurs)
Cardiac Output



Cardiac output (CO)
o Amount of blood pumped by each side (ventricle) of the heart in one minute
Stroke volume (SV)
o Volume of blood pumped by each ventricle in one contraction (each heartbeat)
o About 70 ml of blood is pumped out of the left ventricle with each heartbeat
Heart rate (HR)
o Typically 75 beats per minute
Cardiac Output



CO = HR × SV
CO = HR (75 beats/min) × SV (70 ml/beat)
CO = 5250 ml/min = 5.25 L/min
Regulation of Stroke Volume



60 percent of blood in ventricles (about 70 ml) is pumped with each heartbeat
Starling’s law of the heart:
o Critical factor controlling SV
o The more the cardiac muscle is stretched, the stronger the contraction
SV rises or falls with the volume of venous return
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Regulation of Heart Rate

Heart rate is modified by:
1. Neural (ANS) controls
 Sympathetic nervous system
 Parasympathetic nervous system
2. Hormones and ions
3. Physical factors
Blood Vessels: The Vascular System

Vascular system transports blood to the tissues and back to the heart
o Vessels that carry blood away from the heart:
 Arteries and arterioles
o Vessels that play a role in exchanges between tissues and blood:
 Capillary beds
o Vessels that return blood toward the heart:
 Venules and veins
Microscopic Anatomy of Blood Vessels

Three layers (tunics) in blood vessels (except the capillaries):
o Tunica intima forms a friction-reducing lining
 Endothelium
o Tunica media
 Smooth muscle and elastic tissue
 Controlled by sympathetic nervous system
o Tunica externa forms protective outermost covering
 Mostly fibrous connective tissue
Structural Differences in Arteries, Veins, Capillaries


Arteries have a thicker tunica media than veins to withstand changes in pressure
Veins have a thinner tunica media than arteries and operate under low pressure
o Veins also have valves to prevent backflow of blood
o Lumen of veins is larger than that of arteries
o Skeletal muscle “milks” blood in veins toward the heart
Structural Differences in Arteries, Veins, Capillaries



Capillaries are only one cell layer thick (tunica intima), to allow for exchanges between
blood and tissue
Capillaries form networks called capillary beds
Blood flow through a capillary bed is known as microcirculation
Structural Differences in Arteries, Veins, Capillaries

Capillary beds consist of two types of vessels:
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

1. Vascular shunt
2. True capillaries
Entrances to capillary beds are guarded by precapillary sphincters
Exchanges with tissue cells occur across walls of true capillaries
When precapillary sphincters are closed, blood bypasses the local area via the
vascular shunt
Homeostatic Imbalance

Varicose veins
o Structural defect due to incompetent valves
o Common vascular problem, especially in people who are obese and people
who stand for long periods of time
o Predisposing factor for thrombophlebitis
Major Arteries of the Systemic Circulation

Aorta
o Largest artery in the body
o Leaves from the left ventricle of the heart
o Regions
 Ascending aorta—leaves the left ventricle
 Aortic arch—arches to the left
 Thoracic aorta—travels downward through the thorax
 Abdominal aorta—passes through the diaphragm into the
abdominopelvic cavity
Arterial Branches of the Ascending Aorta

Right and left coronary arteries serve the heart
Arterial Branches of the Aortic Arch



Brachiocephalic trunk splits into the:
o Right common carotid artery
o Right subclavian artery
Left common carotid artery splits into the:
o Left internal and external carotid arteries
Left subclavian artery branches into the:
o Vertebral artery
o In the axilla, the subclavian artery becomes the axillary artery → brachial artery
→ radial and ulnar arteries
Arterial Branches of the Thoracic Aorta


Intercostal arteries supply the muscles of the thorax wall
Other branches of the thoracic aorta supply the (not illustrated):
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o Lungs (bronchial arteries)
o Esophagus (esophageal arteries)
o Diaphragm (phrenic arteries)
Arterial Branches of the Abdominal Aorta


Celiac trunk is the first branch of the abdominal aorta. Three branches are:
1. Left gastric artery (stomach)
2. Splenic artery (spleen)
3. Common hepatic artery (liver)
Superior mesenteric artery supplies most of the small intestine and first half of the
large intestine
Arterial Branches of the Abdominal Aorta



Left and right renal arteries (kidney)
Left and right gonadal arteries
o Ovarian arteries in females serve the ovaries
o Testicular arteries in males serve the testes
Lumbar arteries serve muscles of the abdomen and trunk
Arterial branches of the Abdominal Aorta


Inferior mesenteric artery serves the second half of the large intestine
Left and right common iliac arteries are the final branches of the aorta
o Internal iliac arteries serve the pelvic organs
o External iliac arteries enter the thigh → femoral artery → popliteal artery →
anterior and posterior tibial arteries
Major Veins of Systemic Circulation

Superior and inferior venae cavae enter the right atrium of the heart
o Superior vena cava drains the head and arms
o Inferior vena cava drains the lower body
Veins Draining into the Superior Vena Cava





Radial and ulnar veins → brachial vein → axillary vein
These veins drain the arms
Cephalic vein drains the lateral aspect of the arm and empties into the axillary vein
Basilic vein drains the medial aspect of the arm and empties into the brachial vein
Basilic and cephalic veins are jointed at the median cubital vein (elbow area)
Veins Draining into the Superior Vena Cava

Subclavian vein receives:
o Venous blood from the arm via the axillary vein
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
o Venous blood from skin and muscles via external jugular vein
Vertebral vein drains the posterior part of the head
Internal jugular vein drains the dural sinuses of the brain
Veins Draining into the Superior Vena Cava



Left and right brachiocephalic veins receive venous blood from the:
o Subclavian veins
o Vertebral veins
o Internal jugular veins
Brachiocephalic veins join to form the superior vena cava → right atrium of heart
Azygos vein drains the thorax
Veins Draining into the Inferior Vena Cava




Anterior and posterior tibial veins and fibial veins drain the legs
Posterior tibial vein → popliteal vein → femoral vein → external iliac vein
Great saphenous veins (longest veins of the body) receive superficial drainage of the
legs
Each common iliac vein (left and right) is formed by the union of the internal and
external iliac vein on its own side
Veins Draining into the Inferior Vena Cava





Right gonadal vein drains the right ovary in females and right testicle in males
Left gonadal vein empties into the left renal vein
Left and right renal veins drain the kidneys
Hepatic portal vein drains the digestive organs and travels through the liver before it
enters systemic circulation
Left and right hepatic veins drain the liver
Arterial Supply of the Brain and the Circle of Willis


Internal carotid arteries divide into:
o Anterior and middle cerebral arteries
 These arteries supply most of the cerebrum
Vertebral arteries join once within the skull to form the basilar artery
o Basilar artery serves the brain stem and cerebellum
Arterial Supply of the Brain and the Circle of Willis

Posterior cerebral arteries form from the division of the basilar artery
o These arteries supply the posterior cerebrum
Arterial Supply of the Brain and the Circle of Willis

Anterior and posterior blood supplies are united by small communicating arterial
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
branches
Result—complete circle of connecting blood vessels called cerebral arterial circle, or
circle of Willis
Hepatic Portal Circulation


The hepatic portal circulation is formed by veins draining the digestive organs, which
empty into the hepatic portal vein
o Digestive organs
o Spleen
o Pancreas
Hepatic portal vein carries this blood to the liver, where it is processed before returning
to systemic circulation
Fetal Circulation



Fetal circulation is a temporary circulation seen only in the fetus
Fetus receives exchanges of gases, nutrients, and wastes through the placenta
Umbilical cord contains three vessels:
1. Umbilical vein—carries blood rich in nutrients and oxygen to the fetus
2–3. Umbilical arteries (2)—carry carbon dioxide and debris-laden blood from
fetus to placenta
Fetal Circulation


Shunts bypassing the lungs and liver are also present. Blood flow bypasses the liver
through the ductus venosus and enters the inferior vena cava → right atrium of heart
Blood flow bypasses the lungs
o Blood entering right atrium is shunted directly into left atrium through foramen
ovale (becomes fossa ovalis at or after birth)
o Ductus arteriosus connects aorta and pulmonary trunk (becomes ligamentum
arteriosum at birth)
Arterial Pulse



Pulse
o Alternate expansion and recoil of a blood vessel wall (the pressure wave) that
occurs as the heart beats
Monitored at “pressure points” in superficial arteries where pulse is easily palpated
Pulse averages 70 to 76 beats per minute
at rest, in a healthy person
Blood Pressure

Blood pressure
o The pressure the blood exerts against the inner walls of the blood vessels
o The force that causes blood to continue to flow in the blood vessels
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Blood Pressure Gradient



Blood is forced along a descending pressure gradient
Pressure in blood vessels decreases as distance from the heart increases
Pressure is high in the arteries, lower in the capillaries, and lowest in the veins
Measuring Blood Pressure

Health professionals measure the pressure in large arteries
o Systolic—pressure at the peak of ventricular contraction
o Diastolic—pressure when ventricles relax
o Expressed as systolic pressure over diastolic pressure: for example, 120/80
mm Hg
Effects of Various Factors on Blood Pressure



BP = CO × PR
BP = blood pressure
CO = the amount of blood pumped out of the left ventricle per minute
PR = peripheral resistance, or the amount of friction blood encounters as it flows
through vessels
Effects of Various Factors on Blood Pressure
1. Neural factors: the autonomic nervous system
o Sympathetic nervous system promotes narrowing of vessels (vasoconstriction)
o Vasoconstriction increases blood pressure
Effects of Various Factors on Blood Pressure
2. Renal factors: the kidneys
o Regulation by altering blood volume
o Renin, an enzyme, is released when arterial pressure is low
o Renin triggers formation of angiotensin II, a vasoconstrictor
o Angiotensin II stimulates release of aldosterone
o Aldosterone enhances sodium reabsorption (and water) by kidneys
Effects of Various Factors on Blood Pressure
3. Temperature
o Heat has a vasodilating effect
o Cold has a vasoconstricting effect
4. Chemicals
o Various substances can cause increases or decreases in blood pressure
o Epinephrine increases heart rate and blood pressure
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Effects of Various Factors on Blood Pressure
5. Diet
o Commonly believed that a diet low in salt, saturated fats, and cholesterol
prevents hypertension (high blood pressure)
Variations in Blood Pressure

Normal human range is variable
o Normal
 140 to 110 mm Hg systolic
 80 to 70 mm Hg diastolic
Variations in Blood Pressure
o Hypotension (low blood pressure)
 Low systolic (below 100 mm Hg)
 Often associated with illness
 Acute hypotension is a warning sign for circulatory shock
o Hypertension (high blood pressure)
 Sustained elevated arterial pressure of 140/90 mm Hg
 Warns of increased peripheral resistance
Capillary Exchange of Gases & Nutrients


Substances move to and from the blood and tissue cells through capillary walls
o Exchange is due to concentration gradients
 Oxygen and nutrients leave the blood and move into tissue cells
 Carbon dioxide and other wastes exit tissue cells and enter the blood
Recall that interstitial fluid (tissue fluid) is found between cells
Capillary Exchange of Gases & Nutrients

Substances take various routes entering or leaving the blood:
1. Direct diffusion through membranes
2. Diffusion through intercellular clefts
3. Diffusion through pores of fenestrated capillaries
4. Transport via vesicles
Fluid Movements at Capillary Beds

Whether fluid moves out of or into a capillary depends on the difference between the
two pressures:
1. Blood pressure forces fluid and solutes out of capillaries
2. Osmotic pressure draws fluid into capillaries
Fluid Movements at Capillary Beds
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

Blood pressure is higher than osmotic pressure at the arterial end of the capillary bed
Blood pressure is lower than osmotic pressure at the venous end of the capillary bed
Developmental Aspects of the Cardiovascular System




A simple “tube heart” develops in the embryo and pumps by week 4
The heart becomes a four-chambered organ by the end of 7 weeks
Few structural changes occur after week 7
Congenital heart defects account for half of all infant deaths resulting from congenital
problems
Developmental Aspects of the Cardiovascular System

Age-related problems associated with the cardiovascular system include:
o Weakening of venous valves
o Varicose veins
o Progressive arteriosclerosis
o Hypertension resulting from loss of elasticity of vessels
o Coronary artery disease resulting from fatty, calcified deposits in the vessels
Developmental Aspects of the Cardiovascular System

Modifications in diet (decreased consumption of fats, cholesterol, and salt), stopping
smoking, and regular aerobic exercise may help to reverse the atherosclerotic
process and prolong life
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Part I: The Lymphatic System


Consists of two semi-independent parts:
1. Lymphatic vessels
2. Lymphoid tissues and organs
Lymphatic system functions
o Transports escaped fluids back to the blood
o Plays essential roles in body defense and resistance to disease
Lymphatic Vessels



Lymph—excess tissue fluid and plasma proteins carried by lymphatic vessels
If fluids are not picked up, edema occurs as fluid accumulates in tissues
Lymphatic vessels pick up excess fluid (lymph) and return it to the blood
Lymphatic Vessels

Lymphatic vessels (lymphatics)
o Form a one-way system toward the heart
Lymphatic Vessels

Lymph capillaries
o Weave between tissue cells and blood capillaries
o Walls overlap to form flaplike minivalves
o Fluid leaks into lymph capillaries
o Capillaries are anchored to connective tissue by filaments
o Higher pressure on the inside closes minivalves
o Fluid is forced along the vessel
Lymphatic Vessels

Lymphatic collecting vessels
o Collect lymph from lymph capillaries
o Carry lymph to and away from lymph nodes
o Return fluid to circulatory veins near the heart
 Right lymphatic duct drains the lymph from the right arm and the right
side of the head and thorax
 Thoracic duct drains lymph from rest of body
Lymphatic Vessels

Lymphatic vessels are similar to veins of the cardiovascular system
o Thin-walled
o Larger vessels have valves
o Low-pressure, pumpless system
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
Lymph transported is aided by:
o Milking action of skeletal muscles
o Pressure changes in thorax during breathing
o Smooth muscle in walls of lymphatics
Lymph Nodes


Lymph nodes filter lymph before it is returned to the blood
Harmful materials that are filtered:
o Bacteria
o Viruses
o Cancer cells
o Cell debris
Lymph Nodes

Defense cells within lymph nodes
o Macrophages—engulf and destroy foreign substances such as bacteria,
viruses, and foreign cells
o Lymphocytes—respond to foreign substances in the lymphatic system
Lymph Nodes



Most are kidney-shaped and less than 1 inch long and are buried in connective
tissue
Cortex (outer part)
o Contains follicles—collections of lymphocytes
o Germinal centers enlarge when antibodies are released by plasma cells
Medulla (inner part)
o Contains phagocytic macrophages
Lymph Nodes

Flow of lymph through nodes
o Lymph enters the convex side through afferent lymphatic vessels
o Lymph flows through a number of sinuses inside the node
o Lymph exits through efferent lymphatic vessels
o Because there are fewer efferent than afferent vessels, flow is slowed
Other Lymphoid Organs

Several other organs contribute to lymphatic function:
o Spleen
o Thymus
o Tonsils
o Peyer’s patches
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Spleen





Located on the left side of the abdomen
Filters blood
Destroys worn-out blood cells
Forms blood cells in the fetus
Acts as a blood reservoir
Thymus Gland



Located low in the throat, overlying the heart
Functions at peak levels only during childhood
Produces hormones (such as thymosin) to program lymphocytes
Tonsils



Small masses of lymphoid tissue around the pharynx
Trap and remove bacteria and other foreign materials
Tonsillitis is caused by congestion with bacteria
Peyer’s Patches



Found in the wall of the small intestine and appendix
Resemble tonsils in structure
Capture and destroy bacteria in the intestine
Mucosa-Associated Lymphoid Tissue (MALT)


Includes
o Peyer’s patches
o Tonsils
o Other small accumulations of lymphoid tissue
Acts as a sentinel to protect respiratory and digestive tracts
Part II: Body Defenses



The body is constantly in contact with bacteria, fungi, and viruses
The body has two defense systems for foreign materials that form the immune
system:
1. Innate (nonspecific) defense system
2. Adaptive (specific) defense system
Immunity—specific resistance to disease
Body Defenses

Innate (nonspecific) defense system
o Mechanisms protect against a variety of invaders
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
o Responds immediately to protect body from foreign materials
Adaptive (specific) defense system
o Specific defense is required for each type of invader
Innate (Nonspecific) Body Defenses


Innate body defenses are mechanical barriers to pathogens (harmful or diseasecausing microorganisms) and include:
o Body surface coverings
 Intact skin
 Mucous membranes
o Specialized human cells
o Chemicals produced by the body
Table 12.1 provides a more detailed summary
Surface Membrane Barriers


Surface membrane barriers provide the first line of defense against the invasion of
microorganisms
Skin and mucous membranes
o Physical barrier to foreign materials
o Also provide protective secretions
1. Acidic pH of the skin inhibits bacterial growth
o Sebum is toxic to bacteria
o Vaginal secretions are very acidic
Surface Membrane Barriers
2. Stomach mucosa has secretions that kill pathogens
o Secretes hydrochloric acid
o Has protein-digesting enzymes
3. Saliva and lacrimal fluid contain lysozyme, an enzyme that destroys
bacteria
4. Mucus traps microogranisms in digestive and respiratory pathways
Internal Defenses: Cells and Chemicals

Cells and chemicals provide a second line of defense
o Natural killer cells
o Inflammatory response
o Phagocytes
o Antimicrobial proteins
o Fever
Natural Killer (NK) Cells
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

Can lyse (disintegrate or dissolve) and kill cancer cells, virus-infected cells
Release a chemical called perforin to target the cell’s membrane and nucleus,
causing disintegration
Inflammatory Response

Triggered when body tissues are injured
o Four most common indicators of acute inflammation:
1. Redness
2. Heat
3. Swelling
4. Pain
Inflammatory Response

Functions of the inflammatory response:
o Prevents spread of damaging agents
o Disposes of cell debris and pathogens through phagocytosis
o Sets the stage for repair
Inflammatory Response

Process of the inflammatory response:
1. Neutrophils migrate to the area of inflammation by rolling along the vessel
wall
2. Neutrophils squeeze through the capillary walls by diapedesis to sites of
inflammation
3. Neutrophils gather in the precise site of tissue injury (positive chemotaxis)
and consume any foreign material present
Phagocytes


Cells such as neutrophils and macrophages engulf foreign material into a vacuole
Vacuole is fused with a lysosome, and enzymes from lysosomes digest the material
Antimicrobial Proteins


Enhance innate defenses by:
o Attacking microorganisms directly
o Hindering reproduction of microorganisms
Most important types are:
o Complement proteins
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o Interferon
Complement Proteins




Complement refers to a group of at least 20 plasma proteins
Complement is activated when these plasma proteins encounter and attach to cells
(known as complement fixation)
Membrane attack complexes (MACs), one result of complement fixation, produce
lesions in cells
Some molecules released are vasodilators and chemotaxis chemicals
Interferon


Proteins secreted by virus-infected cells
Interferons bind to membrane receptors on healthy cell surfaces to interfere with the
ability of viruses to multiply
Fever




Abnormally high body temperature is a systemic response to invasion by
microorganisms
Hypothalamus thermostat can be reset higher by pyrogens (secreted by white blood
cells)
High temperatures inhibit the release of iron and zinc (needed by bacteria) from the
liver and spleen
Fever also increases the speed of repair processes
Adaptive Body Defenses




Adaptive body defenses are the body’s specific defense system, or the third line of
defense
Immune response is the immune system’s response to a threat
Immunology is the study of immunity
Antibodies are proteins that protect from pathogens
Adaptive Body Defenses

Three aspects of adaptive defense:
1. Antigen specific—recognizes and acts against particular foreign substances
2. Systemic—not restricted to the initial infection site
3. Memory—recognizes and mounts a stronger attack on previously
encountered pathogens
Adaptive Body Defenses
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
Types of immunity
o Humoral immunity = antibody-mediated immunity
 Provided by antibodies present in body fluids
o Cellular immunity = cell-mediated immunity
 Targets virus-infected cells, cancer cells, and cells of foreign grafts
Antigens

Antigens (nonself)
o Any substance capable of exciting the immune system and provoking an
immune response
o Examples of common antigens:
 Foreign proteins (strongest)
 Nucleic acids
 Large carbohydrates
 Some lipids
 Pollen grains
 Microorganisms
Antigens

Self-antigens
o Human cells have many surface proteins
o Our immune cells do not attack our own proteins
o The presence of our cells in another person’s body can trigger an immune
response because they are foreign
 Restricts donors for transplants
Antigens



Many small molecules (called haptens or incomplete antigens) are not antigenic, but
link up with our own proteins
The immune system may recognize and respond to a protein-hapten combination
The immune response is harmful rather than protective because it attacks our own
cells
Cells of the Adaptive Defense System: An Overview

Crucial cells of the adaptive system:
1. Lymphocytes—respond to specific antigens:
 B lymphocytes (B cells)
 T lymphocytes (T cells)
2. Antigen-presenting cells (APCs)—help the lymphocytes, but do not respond
to specific antigens
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Lymphocytes

Lymphocytes arise from hemocytoblasts of bone marrow
o T cells develop immunocompetence in the thymus and oversee cell-mediated
immunity
o B cells develop immunocompetence in bone marrow and provide humoral
immunity
Lymphocytes


Immunocompetent lymphocytes seed lymphoid organs, where antigen challenge
occurs, and circulate through blood, lymph, and lymphoid organs
Immunocompetence is signaled by the appearance of antigen-specific receptors on
surfaces of lymphocytes
Antigen-Presenting Cells (APCs)



Engulf antigens and then present fragments of them on their own surfaces, where
they can be recognized by T cells
Major types of cells behaving as APCs:
o Dendritic cells
o Macrophages
o B lymphocytes
When they present antigens, dendritic cells and macrophages activate T cells, which
release chemicals
Macrophages




Arise from monocytes produced in bone marrow
Phagocytize pathogens, along with APCs, and present parts of the antigens on their
surfaces, for recognition by T cells
Widely distributed in lymphoid organs and tend to remain fixed in the lymphoid
organs
Secrete cytokines (proteins important in the immune response)
Humoral (Antibody-Mediated) Immune Response



B lymphocytes with specific receptors bind to a specific antigen
The binding event activates the lymphocyte to undergo clonal selection
A large number of clones is produced (primary humoral response)
Humoral Immune Response


Most B cells become plasma cells
o Produce antibodies to destroy antigens
o Activity lasts for 4 or 5 days
Some B cells become long-lived memory cells capable of mounting a rapid attack
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against the same antigen in subsequent meetings (secondary humoral response)
o These cells provide immunological “memory”
Active and Passive Humoral Immunity

Active immunity
o Occurs when B cells encounter antigens and produce antibodies
o Active immunity can be:
 Naturally acquired during bacterial and viral infections
 Artificially acquired from vaccines
Active and Passive Immunity

Passive immunity
o Occurs when antibodies are obtained from someone else
 Naturally acquired from a mother to her fetus
 Artificially acquired from immune serum or gamma globulin
o Immunological memory does not occur
o Protection provided by “borrowed antibodies”
Active and Passive Immunity

Monoclonal antibodies
o Antibodies prepared for clinical testing for diagnostic services
o Produced from descendants of a single cell line
o Examples of uses for monoclonal antibodies
 Diagnosis of pregnancy
 Treatment after exposure to hepatitis and rabies
Antibodies (Immunoglobulins, or Igs)



Soluble proteins secreted by sensitized B cells (plasma cells)
Carried in blood plasma
Capable of binding specifically to an antigen
Antibodies

Antibody structure
o Four amino acid chains, two heavy and two light, linked by disulfide bonds to
form a T- or Y-shaped molecule
o Each polypeptide chain has a variable and a constant region
 Variable regions form antigen-binding sites, one on each arm of the T
or Y
 Constant regions determine antibody function and class
Antibodies
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
Antibody classes
o Antibodies of each class have slightly different roles and differ structurally and
functionally
o Five major immunoglobulin classes (MADGE):
1. IgM—can fix complement
2. IgA—found mainly in mucus
3. IgD—important in activation of B cell
4. IgG—can cross the placental barrier and fix complement
5. IgE—involved in allergies
Antibody Function

Antibodies inactivate antigens in a number of ways
o Complement fixation
o Neutralization: antibodies bind to specific sites on bacterial exotoxins or on
viruses that can cause cell injury
o Agglutination: antibody-antigen reaction that causes clumping of cells
o Precipitation: cross-linking reaction
Cellular (Cell-Mediated) Immune Response




Antigens must be presented by macrophages to an immunocompetent T cell
(antigen presentation)
Antigen presentation occurs as T cells are sensitized, by binding simultaneously to a
nonself antigen and a self-protein displayed on the surface of a macrophage, or
another type of APC
Clonal selection occurs
Clone members differentiate into effector T cells or memory T cells
Cellular (Cell-Mediated) Immune Response

T cell clones
o Cytotoxic (killer) T cells
 Specialize in killing infected cells
 Insert a toxic chemical (perforin)
Cellular (Cell-Mediated) Immune Response

T cell clones: helper T cells
o Recruit other cells to fight invaders
o Interact directly with B cells bound to an antigen
o Release cytokines, chemicals that enhance the killing activity of macrophages
o Attract other leukocytes into the area
o Stimulate B cells and cytotoxic T cells to grow and divide
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Cellular (Cell-Mediated) Immune Response


T cell clones: regulatory T cells
o Release chemicals to suppress the activity of T and B cells
o Stop the immune response to prevent uncontrolled activity
o A few members of each clone are memory cells
A summary of cells and molecules follows (Table 12.3)
Organ Transplants and Rejection

Major types of grafts
o Autografts—tissue transplanted from one site to another on the same person
o Isografts—tissue grafts from an identical person (identical twin)
o Allografts—tissue taken from an unrelated person (most usual type of graft)
o Xenografts—tissue taken from a different animal species (never successful)
Organ Transplants and Rejection

Blood group and tissue matching is done to ensure the best match possible, and
organ transplant is followed by immunosuppressive therapy
Disorders of Immunity

The most important disorders of the immune system are autoimmune diseases,
allergies, and immunodeficiencies
Autoimmune Diseases



Autoimmune disease occurs when the body’s self-tolerance breaks down
The body produces antibodies and/or sensitized T lymphocytes that attack its own
tissues
Most forms of autoimmune disease result from the appearance of formerly hidden
self-antigens or changes in the structure of self-antigens, and antibodies formed
against foreign antigens that resemble self-antigens
Autoimmune Diseases

Examples of autoimmune diseases
o Rheumatoid arthritis—destroys joints
o Myasthenia gravis—impairs communication between nerves and skeletal
muscles
o Multiple sclerosis—white matter of brain and spinal cord is destroyed
o Graves’ disease—thyroid gland produces excess thyroxine
Autoimmune Diseases

Examples of autoimmune diseases
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o Type I diabetes mellitus—destroys pancreatic beta cells that produce insulin
o Systemic lupus erythematosus (SLE)
 Affects kidney, heart, lung, and skin
o Glomerulonephritis—impairment of renal function
Allergies


Allergies, or hypersensitives, are abnormal, vigorous immune responses
The immune system overreacts to an otherwise harmless antigen, and tissue
destruction occurs
Allergies

Types of allergies
o Immediate hypersensitivity
 Seen in hay fever, hives, and anaphylaxis
 Due to IgE antibodies
o Delayed hypersensitivity
 Contact dermatitis
 Reflects activity of T cells, macrophages, and cytokines
 Symptoms usually appear 1–3 days after contact with antigen
Immunodeficiencies



Result from abnormalities in any immune element
Production or function of immune cells or complement is abnormal
May be congenital or acquired
o Severe combined immunodeficiency disease (SCID) is a congenital disease
o AIDS (acquired immune deficiency syndrome) is caused by a virus that
attacks and cripples the helper T cells
Developmental Aspects of the Lymphatic System and Body Defenses




Lymphatic vessels form by budding off veins.
The thymus and the spleen are the first lymphoid organs to appear in the embryo
Other lymphoid organs remain relatively undeveloped until after birth
The immune response develops around the time of birth
Developmental Aspects of the Lymphatic System and Body Defenses



The ability of immunocompetent cells to recognize foreign antigens is genetically
determined
Stress appears to interfere with normal immune response
Efficiency of immune response wanes in old age, and infections, cancer,
immunodeficiencies, and autoimmune diseases become more prevalent
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Organs of the Respiratory System






Nose
Pharynx
Larynx
Trachea
Bronchi
Lungs—alveoli
Functions of the Respiratory System


Gas exchanges between the blood and external environment
o Occur in the alveoli of the lungs
Passageways to the lungs purify, humidify, and warm the incoming air
The Nose



The only externally visible part of the respiratory system
Air enters the nose through the external nostrils (nares)
Interior of the nose consists of a nasal cavity divided by a nasal septum
The Nose


Olfactory receptors are located in the mucosa on the superior surface
The rest of the cavity is lined with respiratory mucosa, which:
o Moistens air
o Traps incoming foreign particles
The Nose


Lateral walls have projections called conchae
o Increase surface area
o Increase air turbulence within the nasal cavity
The nasal cavity is separated from the oral cavity by the palate
o Anterior hard palate (bone)
o Posterior soft palate (unsupported)
Paranasal Sinuses


Cavities within bones surrounding the nasal cavity are called sinuses
Sinuses are located in the following bones:
o Frontal
o Sphenoid
o Ethmoid
o Maxillary
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Paranasal Sinuses

Functions of the sinuses:
o Lighten the skull
o Act as resonance chambers for speech
o Produce mucus that drains into the nasal cavity
Pharynx (Throat)



Muscular passage from nasal cavity to larynx
Three regions of the pharynx:
1. Nasopharynx—superior region behind nasal cavity
2. Oropharynx—middle region behind mouth
3. Laryngopharynx—inferior region attached to larynx
The oropharynx and laryngopharynx are common passageways for air and food
Pharynx (Throat)


Pharyngotympanic tubes open into the nasopharynx
Tonsils of the pharynx
o Pharyngeal tonsil (adenoid) is located in the nasopharynx
o Palatine tonsils are located in the oropharynx
o Lingual tonsils are found at the base of the tongue
Larynx (Voice Box)



Routes air and food into proper channels
Plays a role in speech
Made of eight rigid hyaline cartilages and a spoon-shaped flap of elastic cartilage
(epiglottis)
Larynx (Voice Box)


Thyroid cartilage
o Largest of the hyaline cartilages
o Protrudes anteriorly (Adam’s apple)
Epiglottis
o Protects the superior opening of the larynx
o Routes food to the posteriorly situated esophagus and routes air toward the
trachea
o When swallowing, the epiglottis rises and forms a lid over the opening of the
larynx
Larynx (Voice Box)

Vocal folds (true vocal cords)
o Vibrate with expelled air
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
The glottis consists of the vocal cords and the slitlike pathway (opening)
Trachea (Windpipe)



4-inch-long tube that connects larynx with bronchi
Walls are reinforced with C-shaped hyaline cartilage, which keeps the trachea patent
Lined with ciliated mucosa
o Cilia beat continuously in the opposite direction of incoming air
o Expel mucus loaded with dust and other debris away from lungs
Main (Primary) Bronchi




Formed by division of the trachea
Each bronchus enters the lung at the hilum (medial depression)
Right bronchus is wider, shorter, and straighter than left
Bronchi subdivide into smaller and smaller branches
Lungs




Occupy most of the thoracic cavity
o Heart occupies central portion called mediastinum
Apex is near the clavicle (superior portion)
Base rests on the diaphragm (inferior portion)
Each lung is divided into lobes by fissures
o Left lung—two lobes
o Right lung—three lobes
Coverings of the Lungs



Serosa covers the outer surface of the lungs
o Pulmonary (visceral) pleura covers the lung surface
o Parietal pleura lines the walls of the thoracic cavity
Pleural fluid fills the area between layers to allow gliding and decrease friction during
breathing
Pleural space (between the layers) is more of a potential space
Bronchial (Respiratory) Tree Divisions


All but the smallest of these passageways have reinforcing cartilage in their walls
Conduits to and from the respiratory zone
o Primary bronchi
o Secondary bronchi
o Tertiary bronchi
o Bronchioles
o Terminal bronchioles
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Respiratory Zone Structures




Respiratory bronchioles
Alveolar ducts
Alveolar sacs
Alveoli (air sacs)
The Respiratory Membrane




Thin squamous epithelial layer lines alveolar walls
Alveolar pores connect neighboring air sacs
Pulmonary capillaries cover external surfaces of alveoli
Respiratory membrane (air-blood barrier)
o On one side of the membrane is air, and on the other side is blood flowing past
o Formed by alveolar and capillary walls
The Respiratory Membrane





Gas crosses the respiratory membrane by diffusion
Oxygen enters the blood
Carbon dioxide enters the alveoli
Alveolar macrophages (“dust cells”) add protection by picking up bacteria, carbon
particles, and other debris
Surfactant (a lipid molecule) coats gas-exposed alveolar surfaces
Four Events of Respiration
1. Pulmonary ventilation—moving air into and out of the lungs (commonly called
breathing)
2. External respiration—gas exchange between pulmonary blood and alveoli
o Oxygen is loaded into the blood
o Carbon dioxide is unloaded from the blood
Four Events of Respiration
3. Respiratory gas transport—transport of oxygen and carbon dioxide via the
bloodstream
4. Internal respiration—gas exchange between blood and tissue cells in systemic
capillaries
Mechanics of Breathing (Pulmonary Ventilation)


Completely mechanical process that depends on volume changes in the thoracic
cavity
Volume changes lead to pressure changes, which lead to the flow of gases to equalize
pressure
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Mechanics of Breathing (Pulmonary Ventilation)

Two phases
o Inspiration = inhalation
 Flow of air into lungs
o Expiration = exhalation
 Air leaving lungs
Mechanics of Breathing (Pulmonary Ventilation)

Inspiration
o Diaphragm and external intercostal muscles contract
o The size of the thoracic cavity increases
o External air is pulled into the lungs as a result of:
 Increase in intrapulmonary volume
 Decrease in gas pressure
o Air is sucked into the lungs
Mechanics of Breathing (Pulmonary Ventilation)

Expiration
o Largely a passive process that depends on natural lung elasticity
o As muscles relax, air is pushed out of the lungs as a result of:
 Decrease in intrapulmonary volume
 Increase in gas pressure
o Forced expiration can occur mostly by contraction of internal intercostal
muscles to depress the rib cage
Mechanics of Breathing (Pulmonary Ventilation)


Normal pressure within the pleural space is always negative (intrapleural pressure)
Differences in lung and pleural space pressures keep lungs from collapsing
o Atelectasis is collapsed lung
o Pneumothorax is the presence of air in the intrapleural space
Respiratory Volumes and Capacities


Normal breathing moves about 500 ml of air with each breath
o This respiratory volume is tidal volume (TV)
Many factors affect respiratory capacity
o A person’s size
o Sex
o Age
o Physical condition
Respiratory Volumes and Capacities
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

Inspiratory reserve volume (IRV)
o Amount of air that can be taken in forcibly over the tidal volume
o Usually around 3,100 ml
Expiratory reserve volume (ERV)
o Amount of air that can be forcibly exhaled after a tidal expiration
o Approximately 1,200 ml
Respiratory Volumes and Capacities

Residual volume
o Air remaining in lung after expiration
o Allows gas exchange to go on continuously, even between breaths, and helps
keep alveoli open (inflated)
o About 1,200 ml
Respiratory Volumes and Capacities


Vital capacity
o The total amount of exchangeable air
o Vital capacity = TV + IRV + ERV
o 4,800 ml in men; 3,100 ml in women
Dead space volume
o Air that remains in conducting zone and never reaches alveoli
o About 150 ml
Respiratory Volumes and Capacities


Functional volume
o Air that actually reaches the respiratory zone
o Usually about 350 ml
Respiratory capacities are measured with a spirometer
Nonrespiratory Air (Gas) Movements


Can be caused by reflexes or voluntary actions
Examples:
o Cough and sneeze—clears lungs of debris
o Crying—emotionally induced mechanism
o Laughing—similar to crying
o Hiccup—sudden inspirations
o Yawn—very deep inspiration
Respiratory Sounds


Sounds are monitored with a stethoscope
Two recognizable sounds can be heard with a stethoscope:
1. Bronchial sounds—produced by air rushing through large passageways such
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as the trachea and bronchi
2. Vesicular breathing sounds—soft sounds of air filling alveoli
External Respiration, Gas Transport, and Internal Respiration


Gas exchanges occur as a result of diffusion
Movement of the gas is toward the area of lower concentration
External Respiration

Oxygen is loaded into the blood
o The alveoli always have more oxygen than the blood
o Oxygen moves by diffusion towards the area of lower concentration
o Pulmonary capillary blood gains oxygen
External Respiration


Carbon dioxide is unloaded out of the blood
o Blood returning from tissues has higher concentrations of carbon dioxide than
air in the alveoli
o Pulmonary capillary blood gives up carbon dioxide to be exhaled
Blood leaving the lungs is oxygen rich and carbon dioxide poor
Gas Transport in the Blood

Oxygen transport in the blood
o Most oxygen travels attached to hemoglobin and forms oxyhemoglobin (HbO2)
o A small dissolved amount is carried in the plasma
Gas Transport in the Blood

Carbon dioxide transport in the blood
o Most carbon dioxide is transported in the plasma as bicarbonate ion (HCO3–)
o A small amount is carried inside red blood cells on hemoglobin, but at different
binding sites from those of oxygen
Gas Transport in the Blood

For carbon dioxide to diffuse out of blood into the alveoli, it must be released from its
bicarbonate form:
o Bicarbonate ions enter RBC
o Combine with hydrogen ions
o Form carbonic acid (H2CO3)
o Carbonic acid splits to form water + CO2
o Carbon dioxide diffuses from blood into alveoli
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Internal Respiration


Exchange of gases between blood and body cells
An opposite reaction to what occurs in the lungs
o Carbon dioxide diffuses out of tissue to blood (called loading)
o Oxygen diffuses from blood into tissue (called unloading)
Neural Regulation of Respiration


Activity of respiratory muscles is transmitted to and from the brain by phrenic and
intercostal nerves
Neural centers that control rate and depth are located in the medulla and pons
o Medulla—sets basic rhythm of breathing and contains a pacemaker
(self-exciting inspiratory center) called the ventral respiratory group (VRG)
o Pons—appears to smooth out respiratory rate
Neural Regulation of Respiration


Normal respiratory rate (eupnea)
o 12 to 15 respirations per minute
Hyperpnea
o Increased respiratory rate, often due to extra oxygen needs
Non-Neural Factors Influencing Respiratory Rate and Depth



Physical factors
o Increased body temperature
o Exercise
o Talking
o Coughing
Volition (conscious control)
Emotional factors such as fear, anger, and excitement
Non-Neural Factors Influencing Respiratory Rate and Depth

Chemical factors: CO2 levels
o The body’s need to rid itself of CO2 is the most important stimulus for breathing
o Increased levels of carbon dioxide (and thus, a decreased or acidic pH) in the
blood increase the rate and depth of breathing
o Changes in carbon dioxide act directly on the medulla oblongata
Non-Neural Factors Influencing Respiratory Rate and Depth

Chemical factors: oxygen levels
o Changes in oxygen concentration in the blood are detected by chemoreceptors
in the aorta and common carotid artery
o Information is sent to the medulla
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o Oxygen is the stimulus for those whose systems have become accustomed to
high levels of carbon dioxide as a result of disease
Non-Neural Factors Influencing Respiratory Rate and Depth

Chemical factors
o Hyperventilation
 Rising levels of CO2 in the blood (acidosis) result in faster, deeper
breathing
 Blows off more CO2 to restore normal blood pH
 May result in apnea and dizziness and lead to alkalosis
Non-Neural Factors Influencing Respiratory Rate and Depth

Chemical factors
o Hypoventilation
 Results when blood becomes alkaline (alkalosis)
 Extremely slow or shallow breathing
 Allows CO2 to accumulate in the blood
Respiratory Disorders: Chronic Obstructive Pulmonary Disease
(COPD)


Exemplified by chronic bronchitis and emphysema
Major causes of death and disability in the United States
Respiratory Disorders: Chronic Obstructive Pulmonary Disease
(COPD)

Features of these diseases
1. Patients almost always have a history of smoking
2. Labored breathing (dyspnea) becomes progressively more severe
3. Coughing and frequent pulmonary infections are common
Respiratory Disorders: Chronic Obstructive Pulmonary Disease
(COPD)

Features of these diseases (continued)
4. Most victims are hypoxic, retain carbon dioxide, and have respiratory acidosis
 Those who acquire infections will ultimately develop respiratory failure
Respiratory Disorders: Chronic Bronchitis



Mucosa of the lower respiratory passages becomes severely inflamed
Excessive mucus production impairs ventilation and gas exchange
Patients become cyanotic and are sometimes called “blue bloaters” as a result of
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chronic hypoxia
Respiratory Disorders: Emphysema


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
Alveoli permanently enlarge as adjacent chambers break through and are destroyed
Chronic inflammation promotes lung fibrosis, and lungs lose elasticity
Patients use a large amount of energy to exhale as exhalation becomes an active
process
Overinflation of the lungs leads to a permanently expanded barrel chest
Cyanosis appears late in the disease; sufferers are often called “pink puffers”
Lung Cancer




Extremely aggressive and metastasizes rapidly
Accounts for one-third of all U.S. cancer deaths
Increased incidence is associated with smoking
Three common types:
1. Squamous cell carcinoma
2. Adenocarcinoma
3. Small cell carcinoma
Developmental Aspects of the Respiratory System

Premature infants have problems keeping their lungs inflated because of a lack of
surfactant in their alveoli. (Surfactant is formed late in pregnancy around 28 to 30
weeks of pregnancy)
o Infant respiratory distress syndrome (IRDS)—surfactant production is
inadequate
Developmental Aspects of the Respiratory System

Significant birth defects affecting the respiratory system:
o Cleft palate
o Cystic fibrosis—oversecretion of thick mucus clogs the respiratory system
Developmental Aspects of the Respiratory System

Respiratory rate changes throughout life
o Newborns: 40 to 80 respirations per minute
o Infants: 30 respirations per minute
o Age 5: 25 respirations per minute
o Adults: 12 to 18 respirations per minute
o Rate often increases somewhat with old age
Developmental Aspects of the Respiratory System

Sudden infant death syndrome (SIDS)
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o
o
o
o
Apparently healthy infant stops breathing and dies during sleep
Some cases are thought to be a problem of the neural respiratory control center
One-third of cases appear to be due to heart rhythm abnormalities
Recent research shows a genetic component
Developmental Aspects of the Respiratory System

Asthma
o Chronically inflamed hypersensitive bronchiole passages
o Respond to irritants with dyspnea, coughing, and wheezing
Developmental Aspects of the Respiratory System

During youth and middle age, most respiratory system problems are a result of
external factors, such as infections and substances that physically block respiratory
passageways
Developmental Aspects of the Respiratory System

Aging effects
o Elasticity of lungs decreases
o Vital capacity decreases
o Blood oxygen levels decrease
o Stimulating effects of carbon dioxide decrease
o Elderly are often hypoxic and exhibit sleep apnea
o More risks of respiratory tract infection
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The Digestive System Functions


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
Ingestion—taking in food
Digestion—breaking food into nutrient molecules
Absorption—movement of nutrients into the bloodstream
Defecation—elimination of indigestible waste
Organs of the Digestive System

Two main groups of organs
o Alimentary canal (gastrointestinal or GI tract)—continuous, coiled, hollow tube
 These organs ingest, digest, absorb, defecate
o Accessory digestive organs
 Includes teeth, tongue, and other large digestive organs
Organs of the Alimentary Canal

The alimentary canal is a continuous, coiled, hollow tube that runs through the ventral
cavity from stomach to anus:
o Mouth
o Pharynx
o Esophagus
o Stomach
o Small intestine
o Large intestine
o Anus
Mouth (Oral Cavity)

Anatomy of the mouth
o The mouth (oral cavity)—mucous membrane–lined cavity
o Lips (labia)—protect the anterior opening
o Cheeks—form the lateral walls
o Hard palate—forms the anterior roof
o Soft palate—forms the posterior roof
o Uvula—fleshy projection of the soft palate
Mouth (Oral Cavity)

Anatomy of the mouth (continued)
o Vestibule—space between lips externally and teeth and gums internally
o Oral cavity proper—area contained by the teeth
o Tongue—attached at hyoid bone and styloid processes of the skull, and by the
lingual frenulum to the floor of the mouth
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Mouth (Oral Cavity)

Anatomy of the mouth (continued)
o Tonsils
 Palatine—located at posterior end of oral cavity
 Lingual—located at the base of the tongue
Mouth

Functions of the mouth
o Mastication (chewing) of food
o Tongue mixes masticated food with saliva
o Tongue initiates swallowing
o Taste buds on the tongue allow for taste
Pharynx

Food passes from the mouth posteriorly into the:
o Oropharynx—posterior to oral cavity
o Laryngopharynx—below the oropharynx and continuous with the esophagus
Pharynx



The pharynx serves as a passageway for food, fluids, and air
Food is propelled to the esophagus by two skeletal muscle layers in the pharynx
o Longitudinal inner layer
o Circular outer layer
Alternating contractions of the muscle layers (peristalsis) propel the food
Esophagus (Gullet)


Anatomy
o About 10 inches long
o Runs from pharynx to stomach through the diaphragm
Physiology
o Conducts food by peristalsis (slow rhythmic squeezing) to the stomach
o Passageway for food only (respiratory system branches off after the pharynx)
Layers of Tissue in the Alimentary Canal Organs

Summary of the four layers from innermost to outermost (detailed next):
1. Mucosa
2. Submucosa
3. Muscularis externa
4. Serosa
Layers of Tissue in the Alimentary Canal Organs
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1. Mucosa
o Innermost, moist membrane consisting of:
 Surface epithelium that is mostly simple columnar tissue (except for
esophagus)
 Small amount of connective tissue
(lamina propria)
 Small smooth muscle layer
o Lines the cavity (known as the lumen)
Layers of Tissue in the Alimentary Canal Organs
2. Submucosa
o Just beneath the mucosa
o Soft connective tissue with blood vessels, nerve endings, mucosa-associated
lymphoid tissue, and lymphatics
Layers of Tissue in the Alimentary Canal Organs
3. Muscularis externa—smooth muscle
o Inner circular layer
o Outer longitudinal layer
4. Serosa—outermost layer of the wall contains
fluid-producing cells
o Visceral peritoneum—innermost layer that is continuous with the outermost
layer
o Parietal peritoneum—outermost layer that lines the abdominopelvic cavity by
way of the mesentery
Alimentary Canal Nerve Plexuses



Two important nerve plexuses serve the alimentary canal
Both are part of the autonomic nervous system
o Submucosal nerve plexus
o Myenteric nerve plexus
Function is to regulate mobility and secretory activity of the GI tract organs
Stomach



The stomach is a C-shaped organ located on the left side of the abdominal cavity
Food enters at the cardioesophageal sphincter from the esophagus
Food empties into the small intestine at the pyloric sphincter (valve)
Stomach

Regions of the stomach
o Cardial part (cardia)—near the heart
o Fundus—expanded portion lateral to the cardiac region
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o Body—midportion
o Pylorus—funnel-shaped terminal end
Stomach


Stomach can stretch and hold 4 L (1 gallon) of food when full
o Rugae—internal folds of the mucosa present when the stomach is empty
External regions
o Lesser curvature—concave medial surface
o Greater curvature—convex lateral surface
Stomach


Layers of peritoneum attached to the stomach
o Lesser omentum—attaches the liver to the lesser curvature
o Greater omentum—attaches the greater curvature to the posterior body wall
 Embedded fat insulates, cushions, and protects abdominal organs
 Lymph follicles contain macrophages
Muscularis externa has a third layer
o Oblique layer helps to churn, mix, and pummel the food

Stomach

Functions of the stomach
o Temporary storage tank for food
o Site of food breakdown
o Chemical breakdown of protein begins
o Delivers chyme (processed food) to the small intestine
Stomach

Structure of the stomach mucosa:
o Simple columnar epithelium dotted by gastric pits that lead to gastric glands
o Mucous cells produce bicarbonate-rich alkaline mucus
o Gastric glands—situated in gastric pits and secrete gastric juice, including:
 Intrinsic factor, which is needed for vitamin B12 absorption in the small
intestine
Stomach

Structure of the stomach mucosa (continued)
o Chief cells—produce protein-digesting enzymes (pepsinogens)
o Parietal cells—produce hydrochloric acid
 Mucous neck cells—produce thin acidic mucus (different from the
mucus produced by cells of the mucosa)
o Enteroendocrine cells—produce a hormone called gastrin
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Small Intestine





The body’s major digestive organ
Longest portion of the alimentary tube (2–4 m or 7–13 feet in a living person)
Site of nutrient absorption into the blood
Muscular tube extending from the pyloric sphincter to the ileocecal valve
Suspended from the posterior abdominal wall by the mesentery
Small Intestine

Subdivisions
o Duodenum
 Attached to the stomach
 Curves around the head of the pancreas
o Jejunum
 Attaches anteriorly to the duodenum
o Ileum
 Extends from jejunum to large intestine
 Meets the large intestine at the ileocecal valve
Small Intestine

Chemical digestion begins in the small intestine
o Enzymes are produced by:
 Intestinal cells
 Pancreas
o Pancreatic ducts carry enzymes to the duodenum
o Bile, formed by the liver, enters the duodenum via the bile duct
Small Intestine

Three structural modifications that increase surface area for food absorption
1. Microvilli—tiny projections of the plasma membrane (create a brush border
appearance)
2. Villi—fingerlike projections formed by the mucosa
 House a capillary bed and lacteal
3. Circular folds (plicae circulares)—deep folds of mucosa and submucosa
Large Intestine



Larger in diameter, but shorter in length at 1.5 m, than the small intestine
Extends from the ileocecal valve to the anus
Subdivisions:
o Cecum
o Appendix
o Colon
o Rectum
o Anal canal
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Large Intestine Anatomy


Cecum—saclike first part of the large intestine
Appendix
o Accumulation of lymphoid tissue that sometimes becomes inflamed
(appendicitis)
o Hangs from the cecum
Large Intestine Anatomy


Colon
o Ascending—travels up right side of abdomen
o Transverse—travels across the abdominal cavity
o Descending—travels down the left side
o Sigmoid—S-shaped region; enters the pelvis
Sigmoid colon, rectum, and anal canal are located in the pelvis
Large Intestine Anatomy



Anal canal ends at the anus
Anus—opening of the large intestine
o External anal sphincter—formed by skeletal muscle and under voluntary
control
o Internal anal sphincter—formed by smooth muscle and involuntarily controlled
o These sphincters are normally closed except during defecation
The large intestine delivers undigestible food residues to the body’s exterior
Large Intestine



Goblet cells produce alkaline mucus to lubricate the passage of feces
Muscularis externa layer is reduced to three bands of muscle called teniae coli
These bands of muscle cause the wall to pucker into haustra (pocketlike sacs)
Accessory Digestive Organs





Teeth
Salivary glands
Pancreas
Liver
Gallbladder
Teeth


Teeth masticate (chew) food into smaller fragments
Humans have two sets of teeth during a lifetime:
1. Deciduous (baby or “milk”) teeth
 A baby has 20 teeth by age 2
 First teeth to appear are the lower central incisors
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Teeth
2. Permanent teeth
o Replace deciduous teeth between the ages of 6 and 12
o A full set is 32 teeth, but some people do not have wisdom teeth (third molars)
o If they do emerge, the wisdom teeth appear between ages of 17 and 25
Classification of Teeth




Incisors—cutting
Canines (eyeteeth)—tearing or piercing
Premolars (bicuspids)—grinding
Molars—grinding
Regions of a Tooth

Two major regions of a tooth
1. Crown
2. Root
Regions of a Tooth
1. Crown—exposed part of tooth above the gingiva (gum)
o Enamel—covers the crown
o Dentin—found deep to the enamel and forms the bulk of the tooth, surrounds
the pulp cavity
o Pulp cavity—contains connective tissue, blood vessels, and nerve fibers (pulp)
o Root canal—where the pulp cavity extends into the root
Regions of a Tooth

Note: The neck is a connector between the crown and root.
o Region in contact with the gum
o Connects crown to root
2. Root
o Cement—covers outer surface and attaches the tooth to the periodontal
membrane (ligament)
o Periodontal membrane holds tooth in place in the bony jaw
Figure 14.10 Longitudinal section of a molar.
Salivary Glands

Three pairs of salivary glands empty secretions into the mouth
1. Parotid glands
 Found anterior to the ears
2. Submandibular glands
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3. Sublingual glands
 Both submandibular and sublingual glands empty saliva into the floor of
the mouth through small ducts
Salivary Glands

Saliva
o Mixture of mucus and serous fluids
o Helps to moisten and bind food together into a mass called a bolus
o Contains salivary amylase to begin starch digestion
o Dissolves chemicals so they can be tasted
Pancreas


Found posterior to the parietal peritoneum
o Mostly retroperitoneal
Extends across the abdomen from spleen to duodenum
Pancreas




Produces a wide spectrum of digestive enzymes that break down all categories of
food
Secretes enzymes into the duodenum
Alkaline fluid introduced with enzymes neutralizes acidic chyme coming from stomach
Hormones produced by the pancreas
o Insulin
o Glucagon
Liver




Largest gland in the body
Located on the right side of the body under the diaphragm
Consists of four lobes suspended from the diaphragm and abdominal wall by the
falciform ligament
Connected to the gallbladder via the common hepatic duct
Liver



Bile is produced by cells in the liver
Bile leaves the liver through the common hepatic duct and enters duodenum through
the bile duct
Bile is a yellow-green, watery solution containing:
o Bile salts and bile pigments (mostly bilirubin from the breakdown of
hemoglobin)
o Cholesterol, phospholipids, and electrolytes
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Liver

Function of bile
o Emulsify fats by physically breaking large fat globules into smaller ones
Gallbladder




Sac found in shallow fossa of liver
When no digestion is occurring, bile backs up the cystic duct for storage in the
gallbladder
During digestion of fatty food, bile is introduced into the duodenum from the
gallbladder
Gallstones are crystallized cholesterol, which can cause blockages
Functions of the Digestive System


Major functions of the digestive system are summarized as:
o Digestion
o Absorption
We will cover 6 more specific processes next
Functions of the Digestive System
1. Ingestion—placing of food into the mouth
2. Propulsion—movement of foods from one region of the digestive system to another
o Peristalsis—alternating waves of contraction and relaxation that squeezes food
along the GI tract
o Segmentation—movement of materials back and forth to foster mixing in the
small intestine
Functions of the Digestive System
3. Food breakdown: mechanical breakdown
o Examples:
 Mixing of food in the mouth by the tongue
 Churning of food in the stomach
 Segmentation in the small intestine
o Mechanical digestion prepares food for further degradation by enzymes
Functions of the Digestive System
4. Food breakdown: digestion
o Digestion occurs when enzymes chemically break down large molecules into
their building blocks
o Each major food group uses different enzymes
 Carbohydrates are broken to monosaccharides (simple sugars)
 Proteins are broken to amino acids
 Fats are broken to fatty acids and glycerol
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Functions of the Digestive System
5. Absorption
o End products of digestion are absorbed in the blood or lymph
o Food must enter mucosal cells and then into blood or lymph capillaries
6. Defecation
o Elimination of indigestible substances from the GI tract in the form of feces
Activities Occurring in the Mouth, Pharynx, and Esophagus

Food ingestion and breakdown
o Food is placed into the mouth
 Physically broken down by chewing
 Mixed with saliva, which is released in response to mechanical pressure
and psychic stimuli
 Salivary amylase begins starch digestion
o Essentially, no food absorption occurs in the mouth
Activities Occurring in the Mouth, Pharynx, and Esophagus

Food propulsion—swallowing and peristalsis
o Pharynx and esophagus have no digestive function
 Serve as passageways to the stomach
o Pharynx functions in swallowing (deglutition)
 Two phases of swallowing:
1. Buccal phase
2. Pharyngeal-esophgeal phase
Activities Occurring in the Mouth, Pharynx, and Esophagus

Food propulsion—swallowing and peristalsis (continued)
1. Buccal phase
 Voluntary
 Occurs in the mouth
 Food is formed into a bolus
 The bolus is forced into the pharynx by the tongue
Activities Occurring in the Mouth, Pharynx, and Esophagus

Food propulsion—swallowing and peristalsis (continued)
2. Pharyngeal-esophageal phase
 Involuntary transport of the bolus by peristalsis
 Nasal and respiratory passageways are blocked
Activities Occurring in the Mouth, Pharynx, and Esophagus

Food propulsion—swallowing and peristalsis (continued)
2. Pharyngeal-esophogeal phase (continued)
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

Peristalsis moves the bolus toward the stomach
The cardioesophageal sphincter is opened when food presses against it
Activities in the Stomach

Food breakdown
o Gastric juice is regulated by neural and hormonal factors
o Presence of food or rising pH causes the release of the hormone gastrin
o Gastrin causes stomach glands to produce:
 Protein-digesting enzymes
 Mucus
 Hydrochloric acid
Activities in the Stomach

Food breakdown (continued)
o Hydrochloric acid makes the stomach contents very acidic
o Acidic pH
 Activates pepsinogen to pepsin for protein digestion
 Provides a hostile environment for microorganisms
Activities in the Stomach

Food breakdown (continued)
o Protein digestion enzymes
 Pepsin—an active protein-digesting enzyme
 Rennin—works on digesting milk protein in infants, not adults
o Alcohol and aspirin are virtually the only items absorbed in the stomach
Activities in the Stomach

Food propulsion
1. Peristalsis: Waves of peristalsis occur from the fundus to the pylorus, forcing
food past the pyloric sphincter
2. Grinding: The pylorus meters out chyme into the small intestine (3 ml at a time)
3. Retropulsion: Peristaltic waves close the pyloric sphincter, forcing content back
into the stomach. The stomach empties in 4–6 hours
Activities of the Small Intestine

Food breakdown and absorption
o Intestinal enzymes from the brush border function to:
 Break double sugars into simple sugars
 Complete some protein digestion
o Intestinal enzymes and pancreatic enzymes help to complete digestion of all
food groups
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Activities of the Small Intestine

Food breakdown and absorption (continued)
o Pancreatic enzymes play the major role in the digestion of fats, proteins, and
carbohydrates
o Alkaline content neutralizes acidic chyme and provides the proper environment
for the pancreatic enzymes to operate
Activities of the Small Intestine

Food breakdown and absorption (continued)
o Release of pancreatic juice from the pancreas into the duodenum is stimulated
by:
 Vagus nerves
 Local hormones that travel via the blood to influence the release of
pancreatic juice (and bile):
o Secretin
o Cholecystokinin (CCK)
Activities of the Small Intestine

Food breakdown and absorption (continued)
o Hormones (secretin and CCK) also target the liver and gallbladder to release
bile
 Bile
o Acts as a fat emulsifier
o Needed for fat absorption and absorption of fat-soluble vitamins
(K, D, E, and A)
Activities of the Small Intestine

Food breakdown and absorption (continued)
o A summary table of hormones is presented next
Activities of the Small Intestine

Food breakdown and absorption (continued)
o Water is absorbed along the length of the small intestine
o End products of digestion
 Most substances are absorbed by active transport through cell
membranes
 Lipids are absorbed by diffusion
o Substances are transported to the liver by the hepatic portal vein or lymph
Activities of the Small Intestine

Food breakdown and absorption
o Peristalsis is the major means of moving food
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o Segmental movements
 Mix chyme with digestive juices
 Aid in propelling food
Activities of the Large Intestine

Food breakdown and absorption
o No digestive enzymes are produced
o Resident bacteria digest remaining nutrients
 Produce some vitamin K and B
 Release gases
o Water and vitamins K and B are absorbed
o Remaining materials are eliminated via feces
Activities of the Large Intestine

Food breakdown and absorption (continued)
o Feces contains:
 Undigested food residues
 Mucus
 Bacteria
 Water
Activities of the Large Intestine

Propulsion of the residue and defecation
o Sluggish peristalsis begins when food residue arrives
o Haustral contractions are most seen in the large intestine
o Mass movements are slow, powerful movements that occur 3 to 4 times per
day
Activities of the Large Intestine

Propulsion of the residue and defecation (continued)
o Presence of feces in the rectum causes a defecation reflex
 Internal anal sphincter is relaxed
 Defecation occurs with relaxation of the voluntary (external) anal
sphincter
Nutrition and Metabolism


Most foods are used as metabolic fuel
o Foods are oxidized and transformed into adenosine triphosphate (ATP)
o ATP is chemical energy that drives cellular activities
Energy value of food is measured in kilocalories (kcal) or Calories (C)
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Nutrition



Nutrient—substance used by the body for growth, maintenance, and repair
Major nutrients
o Carbohydrates
o Lipids
o Proteins
o Water
Minor nutrients
o Vitamins
o Minerals
Nutrition


A diet consisting of foods from the five food groups normally guarantees adequate
amounts of all the needed nutrients
The five food groups are summarized next in Table 14.2
Dietary Sources of Major Nutrients

Carbohydrates
o Dietary carbohydrates are sugars and starches
o Most are derived from plants such as fruits and vegetables
o Exceptions: lactose from milk and small amounts of glycogens from meats
Dietary Sources of Major Nutrients

Lipids
o Saturated fats from animal products (meats)
o Unsaturated fats from nuts, seeds, and vegetable oils
o Cholesterol from egg yolk, meats, and milk products (dairy products)
Dietary Sources of Major Nutrients

Proteins
o Complete proteins—contain all essential amino acids
 Most are from animal products (eggs, milk, meat, poultry, and fish)
 Essential amino acids: those that the body cannot make and must be
obtained through diet
o Legumes and beans also have proteins, but the proteins are incomplete
Dietary Sources of Major Nutrients

Vitamins
o Most vitamins are used as coenzymes
o Found mainly in fruits and vegetables
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Dietary Sources of Major Nutrients

Minerals
o Mainly important for enzyme activity
o Foods richest in minerals: vegetables, legumes, milk, and some meats
o Iron is important for making hemoglobin
o Calcium is important for building bone, blood clotting, and secretory activities
Metabolism

Metabolism is all of the chemical reactions necessary to maintain life
o Catabolism—substances are broken down to simpler substances; energy is
released
o Anabolism—larger molecules are built from smaller ones
Carbohydrate Metabolism


Carbohydrates are the body’s preferred source to produce cellular energy (ATP)
Glucose (blood sugar)
o Major breakdown product of carbohydrate digestion
o Fuel used to make ATP
Carbohydrate Metabolism

Cellular respiration
o As glucose is oxidized, carbon dioxide, water, and ATP are formed
Carbohydrate Metabolism

Events of three main metabolic pathways of cellular respiration
1. Glycolysis
 Occurs in the cytosol
 Energizes a glucose molecule so it can be split into two pyruvic acid
molecules and yield ATP
Carbohydrate Metabolism

Events of three main metabolic pathways of cellular respiration (continued)
2. Krebs cycle
 Occurs in the mitochondrion
 Produces virtually all the carbon dioxide and water resulting from cellular
respiration
 Yields a small amount of ATP
Carbohydrate Metabolism

Events of three main metabolic pathways of cellular respiration (continued)
3. Electron transport chain
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


Hydrogen atoms removed during glycolysis and the Krebs cycle are
delivered to protein carriers
Hydrogen atoms are split into hydrogen ions and electrons in the
mitochondria
Electrons give off energy in a series of steps to enable the production of
ATP
Carbohydrate Metabolism


Hyperglycemia—excessively high levels of glucose in the blood
o Excess glucose is stored in body cells as glycogen or converted to fat
Hypoglycemia—low levels of glucose in the blood
o Glycogenolysis, gluconeogenesis, and fat breakdown occur to restore normal
blood glucose levels
Fat Metabolism


Fats
o Insulate the body
o Protect organs
o Build some cell structures (membranes and myelin sheaths)
o Provide reserve energy
Excess dietary fat is stored in subcutaneous tissue and other fat depots
o
Fat Metabolism

When carbohydrates are in limited supply, more fats are oxidized to produce ATP
o Excessive fat breakdown causes blood to become acidic (acidosis or
ketoacidosis)
 Breath has a fruity odor
 Common with:
o “No carbohydrate” diets
o Uncontrolled diabetes mellitus
o Starvation
Protein Metabolism



Proteins form the bulk of cell structure and most functional molecules
Proteins are carefully conserved by body cells
Amino acids are actively taken up from blood by body cells
Protein Metabolism


Amino acids are oxidized to form ATP mainly when other fuel sources are not
available
Ammonia, released as amino acids are catabolized, is detoxified by liver cells that
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combine it with carbon dioxide to form urea
The Central Role of the Liver in Metabolism



Liver is the body’s key metabolic organ
Roles in digestion:
o Manufactures bile
o Detoxifies drugs and alcohol
o Degrades hormones
o Produces cholesterol, blood proteins (albumin and clotting proteins)
o Plays a central role in metabolism
Liver can regenerate if part of it is damaged or removed
The Central Role of the Liver in Metabolism

To maintain homeostasis of blood glucose levels, the liver performs:
o Glycogenesis—“glycogen formation”
 Glucose molecules are converted to glycogen and stored in the liver
o Glycogenolysis—“glycogen splitting”
 Glucose is released from the liver after conversion from glycogen
o Gluconeogenesis—“formation of new sugar”
 Glucose is produced from fats and proteins
The Central Role of the Liver in Metabolism

Fats and fatty acids are picked up by the liver
o Some are oxidized to provide energy for liver cells
o The rest are either stored or broken down into simpler compounds and
released into the blood
The Central Role of the Liver in Metabolism

Cholesterol metabolism and transport
o Cholesterol is not used to make ATP
o Functions of cholesterol:
 Structural basis of steroid hormones and vitamin D
 Building block of plasma membranes
o Most cholesterol (85%) is produced in the liver; only 15% is from the diet
The Central Role of the Liver in Metabolism

Cholesterol metabolism and transport (continued)
o Cholesterol and fatty acids cannot freely circulate in the bloodstream
o They are transported by lipoproteins (lipid-protein complexes) known as LDLs
and HDLs
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The Central Role of the Liver in Metabolism

Cholesterol metabolism and transport (continued)
o Low-density lipoproteins (LDLs) transport cholesterol to body cells
 Rated “bad lipoproteins” since they can lead to artherosclerosis
o High-density lipoproteins (HDLs) transport cholesterol from body cells to the
liver
 Rated “good lipoproteins” since cholesterol is destined for breakdown
and elimination
Body Energy Balance


Energy intake = Total energy output
(heat + work + energy storage)
o Energy intake is the energy liberated during food oxidation
 Energy produced during glycolysis, Krebs cycle, and the electron
transport chain
o Energy output
 Energy we lose as heat (60%)
 Energy stored as fat or glycogen
Body Energy Balance

Interference with the body’s energy balance leads to:
o Obesity
o Malnutrition (leading to body wasting)
Regulation of Food Intake


Body weight is usually relatively stable
o Energy intake and output remain about equal
Mechanisms that may regulate food intake
o Levels of nutrients in the blood
o Hormones
o Body temperature
o Psychological factors
Metabolic Rate and Body Heat Production


Nutrients yield different amounts of energy
Energy value is measured in kilocalorie (kcal)
o Carbohydrates and proteins yield 4 kcal/gram
o Fats yield 9 kcal/gram
Basal Metabolic Rate

Basic metabolic rate (BMR)—amount of heat produced by the body per unit of time at
rest
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
Average BMR is about 60 to 72 kcal/hour for an average 70-kg (154-lb) adult
Basal Metabolic Rate

Factors that influence BMR
o Surface area—a small body usually has a higher BMR
o Gender—males tend to have higher BMRs
o Age—children and adolescents have higher BMRs
o The amount of thyroxine produced is the most important control factor
 More thyroxine means a higher metabolic rate
Total Metabolic Rate (TMR)



TMR—total amount of kilocalories the body must consume to fuel ongoing activities
TMR increases dramatically with an increase in muscle activity
TMR must equal calories consumed to maintain homeostasis and maintain a constant
weight
Body Temperature Regulation


When foods are oxidized, more than 60% of energy escapes as heat, warming the
body
The body has a narrow range of homeostatic temperature
o Must remain between 35.6°C and 37.8°C (96°F and 100°F)
Body Temperature Regulation


The body’s thermostat is in the hypothalamus
Hypothalamus initiates mechanisms to maintain body temperature
o Heat-loss mechanisms involve radiation of heat from skin and evaporation of
sweat
o Heat-promoting mechanisms involve vasoconstriction of skin blood vessels
and shivering
Body Temperature Regulation

Fever—controlled hyperthermia
o Results from infection, cancer, allergic reactions, CNS injuries
o If the body thermostat is set too high, body proteins may be denatured, and
permanent brain damage may occur
Developmental Aspects of the Digestive System and Metabolism



The alimentary canal is a continuous, hollow tube present by the fifth week of
development
Digestive glands bud from the mucosa of the alimentary tube
The developing fetus receives all nutrients through the placenta
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
In newborns, feeding must be frequent, peristalsis is inefficient, and vomiting is
common
Developmental Aspects of the Digestive System and Metabolism


Common congenital defects that interfere with normal nutrition:
o Cleft palate
o Cleft lip
o Tracheoesophageal fistula
Common inborn errors of metabolism:
o Phenylketonuria (PKU)
o Cystic fibrosis (CF)
Developmental Aspects of the Digestive System and Metabolism


Newborn reflexes
o Rooting reflex helps the infant find the nipple
o Sucking reflex helps the infant hold on to the nipple and swallow
Teething begins around age 6 months
Developmental Aspects of the Digestive System and Metabolism



Problems of the digestive system:
o Gastroenteritis—inflammation of the gastrointestinal tract; can occur at any
time
o Appendicitis—inflammation of the appendix; common in adolescents
Metabolism decreases with old age
Middle-age digestive problems
o Ulcers
o Gallbladder problems
Developmental Aspects of the Digestive System and Metabolism


Later middle-age problems
o Obesity
o Diabetes mellitus
Activity of the digestive tract in old age
o Fewer digestive juices
o Peristalsis slows
o Diverticulosis and gastrointestinal cancers are more common
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Functions of the Urinary System

Elimination of waste products
o Nitrogenous wastes
o Toxins
o Drugs
Functions of the Urinary System

Regulation of aspects of homeostasis
o Water balance
o Electrolytes
o Acid-base balance in the blood
o Blood pressure
o Red blood cell production
o Activation of vitamin D
Organs of the Urinary System




Kidneys
Ureters
Urinary bladder
Urethra
Kidneys

Location and structure
o The kidneys are situated against the dorsal body wall in a retroperitoneal
position (behind the parietal peritoneum)
o The kidneys are situated at the level of the T12 to L3 vertebrae
o The right kidney is slightly lower than the left (because of position of the liver)
Kidneys

Location and structure (continued)
o Renal hilum
 A medial indentation where several structures enter or exit the kidney
(ureters, renal blood vessels, and nerves)
o An adrenal gland sits atop each kidney
Kidneys

Location and structure (continued)
o Fibrous capsule encloses each kidney
o Perirenal fat capsule surrounds the kidney and cushions against blows
o Renal fascia is the outermost capsule that anchors the kidney and adrenal
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gland to surrounding structures
Kidneys

Location and structure (continued)
o Three regions revealed in a longitudinal section:
1. Renal cortex—outer region
2. Renal medulla—deeper region
o Renal (medullary) pyramids—triangular regions of tissue in the
medulla
o Renal columns—extensions of cortex-like material that separate
the pyramids
Kidneys

Location and structure (continued)
o Three regions:
3. Renal pelvis—medial region that is a flat, funnel-shaped tube
o Calyces—cup-shaped extensions of the renal pelvis that enclose
the renal pyramids
o Calyces collect urine and send it to the renal pelvis, on to the
ureter, and to the urinary bladder for storage
Blood Supply



One-quarter of the total blood supply of the body passes through the kidneys each
minute
Renal artery provides each kidney with arterial blood supply
Renal artery divides into segmental arteries  interlobar arteries  arcuate arteries
 cortical radiate arteries
Blood Supply

Venous blood flow
o Cortical radiate veins  arcuate veins
o There are no segmental veins
o Renal vein returns blood to the inferior vena cava
Nephrons


Nephrons:
o Structural and functional units of the kidneys
o Responsible for forming urine
Each nephron consists of two main structures:
1. Renal corpuscle
2. Renal tubule
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 inte rloba r ve ins  re
Nephrons

Renal corpuscle consists of:
1. Glomerulus, a knot of capillaries made of podocytes
 Podocytes have filtration slits and foot processes that stick to the
glomerulus
2. Glomerular (Bowman’s) capsule surrounds the glomerulus
 First part of the renal tubule
Nephrons


Renal tubule extends from glomerular capsule and ends when it empties into the
collecting duct
From the glomerular (Bowman’s) capsule, the subdivisions of the renal tubule are:
1. Proximal convoluted tubule (PCT)
2. Nephron loop (loop of Henle)
3. Distal convoluted tubule (DCT)
Nephrons



Cortical nephrons
o Located entirely in the cortex
o Include most nephrons
Juxtamedullary nephrons
o Found at the boundary of the cortex and medulla
o Nephron loop dips deep into the medulla
Collecting ducts collect urine from both types of nephrons, through the renal pyramids,
to the calyces, and then to the renal pelvis
Nephrons

Two capillary beds associated with each nephron:
1. Glomerulus
2. Peritubular capillary bed
Nephrons

Glomerulus
o Fed and drained by arterioles
 Afferent arteriole—arises from a cortical radiate artery and feeds the
glomerulus
 Efferent arteriole—receives blood that has passed through the
glomerulus
o Specialized for filtration
o High pressure forces fluid and solutes out of blood and into the glomerular
capsule
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Nephrons

Peritubular capillary beds
o Arise from efferent arteriole of the glomerulus
o Normal, low-pressure, porous capillaries
o Adapted for absorption instead of filtration
o Cling close to the renal tubule to reabsorb (reclaim) some substances from
collecting tubes
o Drain into the interlobar veins
Urine Formation

Urine formation is the result of three processes:
1. Glomerular filtration
2. Tubular reabsorption
3. Tubular secretion
Glomerular Filtration


The glomerulus is a filter
Filtration is a nonselective passive process
o Water and solutes smaller than proteins are forced through capillary walls
o Proteins and blood cells are normally too large to pass through the filtration
membrane
o Filtrate is collected in the glomerular capsule and leaves via the renal tubule
Glomerular Filtration



Filtrate will be formed as long as systemic blood pressure is normal
o If arterial blood pressure is too low, filtrate formation stops because glomerular
pressure will be too low to form filtrate
Oligouria is abnormally low urine output (between 100 and 400 ml per day)
Anuria is less than 100 ml of urine produced per day
Tubular Reabsorption



The peritubular capillaries reabsorb useful substances from the renal tubule cells,
such as:
o Water
o Glucose
o Amino acids
o Ions
Some reabsorption is passive; most is active
Most reabsorption occurs in the proximal convoluted tubule
Tubular Reabsorption

Nitrogenous waste products are poorly reabsorbed, if at all
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o Urea—end product of protein breakdown
o Uric acid—results from nucleic acid breakdown
o Creatinine—associated with creatine metabolism in muscles
Tubular Secretion


Tubular secretion is reabsorption in reverse
Some materials move from the blood of the peritubular capillaries into the renal
tubules
o Hydrogen and potassium ions
o Creatinine
Tubular Secretion


Secretion is important for:
o Getting rid of substances not already in the filtrate
o Removing drugs and excess ions
o Maintaining acid-base balance of blood
Materials left in the renal tubule move toward the ureter
Characteristics of Urine


In 24 hours, about 1.0 to 1.8 liters of urine are produced
Urine and filtrate are different
o Filtrate contains everything that blood plasma does (except proteins)
o Urine is what remains after the filtrate has lost most of its water, nutrients, and
necessary ions through reabsorption
o Urine contains nitrogenous wastes and substances that are not needed
Characteristics of Urine





Yellow color due to the pigment urochrome (from the destruction of hemoglobin) and
solutes
o Dilute urine is a pale, straw color
Sterile
Slightly aromatic
Normal pH of around 6 (slightly acidic)
Specific gravity of 1.001 to 1.035
Characteristics of Urine

Solutes normally found in urine
o Sodium and potassium ions
o Urea, uric acid, creatinine
o Ammonia
o Bicarbonate ions
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Characteristics of Urine

Solutes NOT normally found in urine
o Glucose
o Blood proteins
o Red blood cells
o Hemoglobin
o Pus (WBCs)
o Bile
Ureters



Slender tubes attaching the kidney to the urinary bladder
o Continuous with the renal pelvis
o Enter the posterior aspect of the urinary bladder
Runs behind the peritoneum
Peristalsis aids gravity in urine transport
Urinary Bladder




Smooth, collapsible, muscular sac situated posterior to the pubic symphysis
Temporarily stores urine
Trigone—triangular region of the urinary bladder base
o Three openings
 Two from the ureters
 One to the urethra
In males, the prostate surrounds the neck of the urinary bladder
Urinary Bladder

Wall of the urinary bladder:
o Three layers of smooth muscle collectively called the detrusor muscle
o Mucosa made of transitional epithelium
o Walls are thick and folded in an empty urinary bladder
o Urinary bladder can expand significantly without increasing internal pressure
Urinary Bladder

Capacity of the urinary bladder
o A moderately full bladder is about 5 inches long and holds about 500 ml of urine
o Capable of holding twice that amount of urine
Urethra


Thin-walled tube that carries urine from the urinary bladder to the outside of the body
by peristalsis
Function
o Females—only carries urine
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o Males—carries urine and sperm
Urethra

Release of urine is controlled by two sphincters
1. Internal urethral sphincter
 Involuntary and made of smooth muscle
2. External urethral sphincter
 Voluntary and made of skeletal muscle
Urethra


Length
o In females: 3 to 4 cm (1 inch)
o In males: 20 cm (8 inches)
Location
o Females—anterior to the vaginal opening
o Males—travels through the prostate and penis
 Prostatic urethra
 Membranous urethra
 Spongy urethra
Urethra



Urethritis is inflammation of the urethra
Cystitis is bladder inflammation
Pyelonephritis (pyelitis) is kidney inflammation
Micturition (Voiding)





Micturition is emptying of the urinary bladder
Micturition reflex causes the involuntary internal sphincter to open when stretch
receptors in the bladder are stimulated
The external sphincter is voluntarily controlled, so micturition can usually be delayed
Incontinence is the inability to control micturition
Urinary retention is the inability to empty the bladder
Fluid, Electrolyte, and Acid-Base Balance

Blood composition depends on three factors
1. Diet
2. Cellular metabolism
3. Urine output
Fluid, Electrolyte, and Acid-Base Balance

Kidneys have four roles in maintaining blood composition
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1.
2.
3.
4.
Excretion of nitrogen-containing wastes (previously discussed)
Maintaining water balance of the blood
Maintaining electrolyte balance of the blood
Ensuring proper blood pH
Bodily Fluids and Fluid Compartments


Normal amount of water in the human body
o Young adult females = 50%
o Young adult males = 60%
o Babies = 75%
o The elderly = 45%
Water is necessary for many body functions, and levels must be maintained
Bodily Fluids and Fluid Compartments

Water occupies three main fluid compartments
1. Intracellular fluid (ICF)
 Fluid inside cells
 About two-thirds of body fluid
2. and 3. Extracellular fluid (ECF)
 Fluids outside cells; includes:
2. Interstitial fluid
3. Blood plasma, cerebrospinal and serous fluids, humors of the
eye and lymph
The Link Between Water and Salt


Solutes in the body include electrolytes such as sodium, potassium, and calcium ions
Changes in electrolyte balance causes water to move from one compartment to
another
o Alters blood volume and blood pressure
o Can impair the activity of cells
Regulation of Water Intake and Output



Water intake must equal water output if the body is to remain properly hydrated
Sources for water intake
o Ingested foods and fluids
o Water produced from metabolic processes
Thirst mechanism is the driving force for water intake
Regulation of Water Intake and Output

Thirst mechanism
o Osmoreceptors are sensitive cells in the hypothalamus that react to small
changes in blood composition by becoming more active
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o When activated, the thirst center in the hypothalamus is notified
o A dry mouth due to decreased saliva also promotes the thirst mechanism
o Both reinforce the drive to drink
Regulation of Water Intake and Output

Sources of water output
o Lungs (insensible since we cannot sense the water leaving)
o Perspiration
o Feces
o Urine
Regulation of Water Intake and Output

Hormones are primarily responsible for reabsorption of water and electrolytes by the
kidneys
o Antidiuretic hormone (ADH) prevents excessive water loss in the urine and
increases water reabsorption
o Diabetes insipidus results when ADH is not released
 Leads to severe dehydration and electrolyte imbalances
Electrolyte Balance

Hormones are primarily responsible for reabsorption of water and electrolytes by the
kidneys
o Aldosterone increases sodium and water reabsorption and decreases
potassium reabsorption
o Water follows salt: when sodium is reabsorbed, water follows it passively back
into the blood
Electrolyte Balance

Renin-angiotensin mechanism
o Important for regulating blood pressure
o Mediated by the juxtaglomerular (JG) apparatus of the renal tubules
o When cells of the JG apparatus are stimulated by low blood pressure, the
enzyme renin is released into blood
Electrolyte Balance

Renin-angiotensin mechanism (continued)
o Renin catalyzes reactions that produce angiotensin II
o Angiotensin II causes vasoconstriction and aldosterone release
o Result is increase in blood volume and blood pressure
Maintaining Acid-Base Balance in Blood
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
Blood pH must remain between 7.35 and 7.45 to maintain homeostasis
o Alkalosis—pH above 7.45
o Acidosis—pH below 7.35
o Physiological acidosis—pH between 7.35 and 7.0
Maintaining Acid-Base Balance in Blood


Kidneys play greatest role in maintaining acid-base balance
Other acid-base controlling systems
o Blood buffers
o Respiration
Blood Buffers


Acids are proton (H+) donors
o Strong acids dissociate completely and liberate all of their H+ in water
o Weak acids, such as carbonic acid, dissociate only partially
Bases are proton (H+) acceptors
o Strong bases dissociate easily in water and
tie up H+
o
Weak bases, such as bicarbonate ion and ammonia, are slower to accept H+
Blood Buffers


Molecules react to prevent dramatic changes in hydrogen ion (H+) concentrations
o Bind to H+ when pH drops
o Release H+ when pH rises
Three major chemical buffer systems
1. Bicarbonate buffer system
2. Phosphate buffer system
3. Protein buffer system
Blood Buffers

The bicarbonate buffer system
o Mixture of carbonic acid (H2CO3) and sodium bicarbonate (NaHCO3)
 Carbonic acid is a weak acid that does not dissociate much in neutral or
acid solutions
 Bicarbonate ions (HCO3–) react with strong acids to change them to
weak acids
HCl
+
strong acid
NaHCO3 
weak base
H2CO3
weak acid
+
NaCl
salt
Blood Buffers

The bicarbonate buffer system (continued)
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o Carbonic acid dissociates in the presence of a strong base to form a weak base
and water
NaOH
+
strong base
H2CO3
weak acid

NaHCO3
weak base
+
H2O
water
Respiratory System Controls

Respiratory rate can rise and fall depending on changing blood pH to retain CO2
(decreasing the blood pH) or remove CO2 (increasing the blood pH)
CO2 + H2O  H2CO3  H+ + HCO3−
Renal Mechanisms



When blood pH rises:
o Bicarbonate ions are excreted
o Hydrogen ions are retained by kidney tubules
When blood pH falls:
o Bicarbonate ions are reabsorbed
o Hydrogen ions are secreted
Urine pH varies from 4.5 to 8.0
Developmental Aspects of the Urinary System



The kidneys begin to develop in the first few weeks of embryonic life and are excreting
urine by the third month of fetal life
Common congenital abnormalities include polycystic kidney and hypospadias
Common urinary system problems in children and young to middle-aged adults
include infections caused by fecal microorganisms, microorganisms causing sexually
transmitted infections, and Streptococcus

Developmental Aspects of the Urinary System



Control of the voluntary urethral sphincter does not start until age 18 months
Complete nighttime control may not occur until the child is 4 years old
Urinary tract infections (UTIs) are the only common problems before old age
o Escherichia coli (E. coli), a bacterium, accounts for 80 percent of UTIs
Developmental Aspects of the Urinary System


Renal failure is an uncommon but serious problem in which the kidneys are unable to
concentrate urine, and dialysis must be done to maintain chemical homeostasis of
blood
With age, filtration rate decreases and tubule cells become less efficient at
concentrating urine, leading to urgency, frequency, and incontinence
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
In men, urinary retention is another common problem
Developmental Aspects of the Urinary System

Problems associated with aging:
o Urgency—feeling that it is necessary to void
o Frequency—frequent voiding of small amounts of urine
o Nocturia—need to get up during the night to urinate
o Incontinence—loss of control
o Urinary retention—common in males, often the result of hypertrophy of the
prostate gland
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The Reproductive System


Gonads—primary sex organs
o Testes in males
o Ovaries in females
Gonads produce gametes (sex cells) and secrete hormones
o Sperm—male gametes
o Ova (eggs)—female gametes
Anatomy of the Male Reproductive System


Testes
Duct system
o Epididymis
o Ductus (vas) deferens
o Urethra
Anatomy of the Male Reproductive System


Accessory organs
o Seminal glands (vesicles)
o Prostate
o Bulbo-urethral glands
External genitalia
o Penis
o Scrotum
Testes

Coverings of the testes
o Tunica albuginea—capsule that surrounds each testis
o Septa—extensions of the capsule that extend into the testis and divide it into
lobules
Testes



Each lobule contains one to four seminiferous tubules
o Tightly coiled structures
o Function as sperm-forming factories
o Empty sperm into the rete testis (first part of the duct system)
Sperm travels through the rete testis to the epididymis
Interstitial cells in the seminiferous tubules produce androgens such as testosterone
Duct System

The duct system transports sperm from the body and includes:
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o Epididymis
o Ductus (vas) deferens
o Urethra
Duct System

Epididymis
o Comma-shaped, tightly coiled tube
o Found on the superior part of the testis and along the posterior lateral side
o Sperm cells mature and gain the ability to swim over the course of 20 days in
the epididymis
o Sperm are expelled with the contraction of muscles in the epididymis walls to
the ductus deferens
Duct System

Ductus (vas) deferens
o Carries sperm from the epididymis to the ejaculatory duct
o Passes through the inguinal canal and over the urinary bladder
o Moves sperm by peristalsis
o Spermatic cord—ductus deferens, blood vessels, and nerves in a connective
tissue sheath
Duct System

Ductus (vas) deferens
o Ejaculation—smooth muscle in the walls of the ductus deferens create
peristaltic waves to squeeze sperm forward
o Vasectomy—cutting of the ductus deferens at the level of the testes prevents
transportation of sperm (form of birth control)
Duct System

Urethra
o Extends from the base of the urinary bladder to the tip of the penis
o Carries both urine and sperm
o Sperm enters from the ejaculatory duct
Duct System

Urethra regions
1. Prostatic urethra—surrounded by prostate
2. Intermediate (membranous) urethra—travels from prostatic urethra to penis
3. Spongy (penile) urethra—runs the length of the penis to the external urethral
orifice
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Accessory Glands and Semen



Seminal glands (vesicles)
Prostate
Bulbo-urethral glands
Accessory Glands and Semen

Seminal glands (vesicles)
o Located at the base of the bladder
o Produce a thick, yellowish secretion (60% of semen) that contains:
 Fructose (sugar)
 Vitamin C
 Prostaglandins
 Other substances that nourish and activate sperm
Accessory Glands and Semen

Prostate
o Encircles the upper part of the urethra
o Secretes a milky fluid
 Helps to activate sperm
 Fluid enters the urethra through several small ducts
o Prostatitis–inflammation of the prostate
o Prostate cancer–third most common cancer in males
Accessory Glands and Semen

Bulbo-urethral glands
o Pea-sized glands inferior to the prostate
o Produce a thick, clear mucus
 Mucus cleanses the spongy (penile) urethra of acidic urine prior to
ejaculation
 Mucus serves as a lubricant during sexual intercourse
 Mucus is released into the spongy urethra
Accessory Glands and Semen

Semen
o Milky white mixture of sperm and accessory gland secretions
o Advantages of accessory gland secretions
 Fructose provides energy for sperm cells
 Alkalinity of semen helps neutralize the acidic environment of vagina
 Semen inhibits bacterial multiplication
 Elements of semen enhance sperm motility
External Genitalia
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

Scrotum
Penis
External Genitalia

Scrotum
o Divided sac of skin outside the abdomen that houses the testes
o Maintains testes at 3°C lower than normal body temperature to protect sperm
viability
External Genitalia

Penis
o Delivers sperm into the female reproductive tract
o Regions of the penis
 Shaft
 Glans penis (enlarged tip)
 Prepuce (foreskin)
o Folded cuff of skin around proximal end
o Often removed by circumcision
External Genitalia

Penis (continued)
o Internally there are three areas of spongy erectile tissue around the urethra
o Erections occur when this erectile tissue fills with blood during sexual
excitement
Spermatogenesis



Process of making sperm cells
Begins at puberty and continues throughout life
Sperm are formed in the seminiferous tubules
Spermatogenesis


Spermatogonia (stem cells) undergo rapid mitosis to produce more stem cells before
puberty
During puberty, follicle-stimulating hormone (FSH) is secreted in increasing amounts
Spermatogenesis

Each division of a spermatogonium stem cell produces:
o A stem cell, called a type A daughter cell, that continues the stem cell line
o The other cell produced becomes a primary spermatocyte, called a type B
daughter cell
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Spermatogenesis



Primary spermatocytes undergo two successive divisions known as meiosis
One primary spermatocyte produces four haploid spermatids
o Spermatids—23 chromosomes, n (half as much genetic material as other body
cells)
Union of a sperm (23 chromosomes, n) with an egg (23 chromosomes, n) creates a
zygote (2n, or 46 chromosomes)
Spermatogenesis

Spermiogenesis
o Streaming process that strips excess cytoplasm from a spermatid and modifies
it into a sperm
o Mature sperm is compacted into three regions: head, midpiece, tail
o The entire process of spermatogenesis, including spermiogenesis, takes 64 to
72 days
Testosterone Production


Testosterone is the most important hormone of the testes
o Produced by interstitial cells in the testes
During puberty, luteinizing hormone (LH) from the anterior pituitary activates the
interstitial cells
o In turn, testosterone is produced
Testosterone Production

Testosterone
o Stimulates reproductive organ development
o Underlies sex drive
o Causes secondary sex characteristics
 Deepening of voice
 Increased hair growth
 Enlargement of skeletal muscles
 Increased bone growth and density
Anatomy of the Female Reproductive System



Ovaries
Duct system
o Uterine (fallopian) tubes
o Uterus
o Vagina
External genitalia
Ovaries
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

The ovaries house many ovarian follicles (sac-like structures)
Each follicle consists of:
o Oocyte (immature egg)
o Follicle cells—layers of different cells that surround the oocyte
Ovaries


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Primary follicle—contains an immature oocyte
Vesicular (Graafian) follicle—growing follicle with a maturing oocyte
Ovulation—the follicle ruptures when the egg is mature and ready to be ejected from
the ovary; occurs about every 28 days
The ruptured follicle is transformed into a corpus luteum
Ovaries



Suspensory ligaments secure the ovaries to the lateral walls of the pelvis
Ovarian ligaments anchor the ovaries to the uterus
Broad ligaments, a fold of peritoneum, enclose and hold the ovaries in place
Duct System



Uterine (fallopian) tubes
Uterus
Vagina
Duct System

Uterine (fallopian) tubes
o Receive the ovulated oocyte from the ovaries
o Provide a site for fertilization
o Empty into the uterus
o Little or no contact between ovaries and uterine tubes
o Supported and enclosed by the broad ligament
Duct System

Uterine (fallopian) tube structure
o Fimbriae
 Fingerlike projections at the distal end of the uterine tube
 Receive the oocyte from the ovary
o Cilia
 Located inside the uterine tube
 Slowly move the oocyte towards the uterus (takes 3 to 4 days)
Duct System

Uterus
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o Pear-shaped muscular organ situated between the urinary bladder and rectum
o Receives, retains, nourishes a fertilized egg
Duct System

Uterus
o Broad ligament suspends the uterus in the pelvis
o Round ligament anchors the uterus anteriorly
o Uterosacral ligament anchors the uterus posteriorly
Duct System

Regions of the uterus:
o Body—main portion
o Fundus—superior rounded region above where uterine tube enters
o Cervix—narrow outlet that protrudes into the vagina
Duct System

Walls of the uterus
o Endometrium
 Inner layer
 Allows for implantation of a fertilized egg
 Sloughs off if no pregnancy occurs (menses)
o Myometrium is the middle layer of smooth muscle that contracts during labor
o Perimetrium (visceral peritoneum) is the outermost serous layer of the uterus
Duct System

Vagina
o Passageway that extends from cervix to exterior of body and is located
between urinary bladder and rectum
o Serves as the canal that allows a baby or menstrual flow to leave the body
o Receives the penis during sexual intercourse
o Hymen—partially closes the vagina until it is ruptured
External Genitalia and Female Perineum

The female external genitalia, or vulva, includes:
o Mons pubis
o Labia
o Clitoris
o Urethral orifice
o Vaginal orifice
o Greater vestibular glands
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External Genitalia and Female Perineum

Mons pubis
o Fatty area overlying the pubic symphysis
o Covered with pubic hair after puberty
External Genitalia and Female Perineum

Labia—skin folds
o Labia majora
 Hair-covered skin folds
 Enclose the labia minora
 Also encloses the vestibule
o Labia minora—delicate, hair-free folds of skin
External Genitalia and Female Perineum


Vestibule
o Enclosed by labia majora
o Contains external openings of the urethra and vagina
Greater vestibular glands
o One is found on each side of the vagina
o Secretes lubricant during intercourse
External Genitalia and Female Perineum

Clitoris
o Contains erectile tissue
o Corresponds to the male penis
o The clitoris is similar to the penis in that it is:
 Hooded by a prepuce
 Composed of sensitive erectile tissue
 Swollen with blood during sexual excitement
External Genitalia and Female Perineum

Perineum
o Diamond-shaped region between the anterior ends of the labial folds, anus
posteriorly, and ischial tuberosities laterally
Female Reproductive Functions and Cycles




The total supply of eggs is determined by the time a female is born
Ability to release eggs begins at puberty
Reproductive ability ends at menopause
Oocytes are matured in developing ovarian follicles
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Oogenesis and the Ovarian Cycle
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Oogenesis is the process of producing ova (eggs) in a female
Oogonia are female stem cells found in a developing fetus
Oogonia undergo mitosis to produce primary oocytes that are surrounded by cells that
form primary follicles in the ovary
Oogenesis and the Ovarian Cycle



Primary oocytes are inactive until puberty
Follicle stimulating hormone (FSH) causes some primary follicles to mature each
month
Cyclic monthly changes constitute the ovarian cycle
Oogenesis and the Ovarian Cycle


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
Meiosis starts inside maturing follicle
Produces a secondary oocyte and the first polar body
Follicle development to the stage of a vesicular follicle takes about 14 days
Ovulation of a secondary oocyte occurs with the release of luteinizing hormone (LH)
Secondary oocyte is released and surrounded by a corona radiata
Oogenesis and the Ovarian Cycle



Meiosis is completed after ovulation only if sperm penetrates the oocyte
o Ovum is produced
o Two additional polar bodies are produced
Once ovum is formed, the 23 chromosomes can be combined with the 23
chromosomes of the sperm to form the fertilized egg (zygote)
If the secondary oocyte is not penetrated by a sperm, it dies and does not complete
meiosis to form an ovum
Male and Female Differences


Meiosis
o Males—produces four functional sperm
o Females—produces one functional ovum and three tiny polar bodies
Sex cell size and structure
o Sperm are tiny, motile, and equipped with nutrients in seminal fluid
o Egg is large, is nonmotile, and has nutrient reserves to nourish the embryo until
implantation
Uterine (Menstrual) Cycle



Cyclic changes of the endometrium about 28 days in length
Regulated by cyclic production of estrogens and progesterone by the ovaries
FSH and LH, from the anterior pituitary, regulate the production of estrogens and
progesterone by the ovaries
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
Ovulation typically occurs about midway through cycle, on day 14
Uterine (Menstrual) Cycle

Stages of the menstrual cycle
o Menstrual phase
o Proliferative stage
o Secretory stage
Uterine (Menstrual) Cycle

Menstrual phase
o Days 1 to 5
o Functional layer of the endometrium is sloughed
o Bleeding occurs for 3 to 5 days
o Ovarian hormones are at their lowest levels
o By day 5, growing ovarian follicles are producing more estrogen
Uterine (Menstrual) Cycle

Proliferative stage
o Days 6 to 14
o Regeneration of functional layer of the endometrium
 Endometrium is repaired, thickens, and becomes well vascularized
o Estrogen levels rise
o Ovulation occurs in the ovary at the end of this stage
Uterine (Menstrual) Cycle

Secretory stage
o Days 15 to 28
o Levels of progesterone rise and increase the blood supply to the endometrium,
which becomes more vascular
 Progesterone is produced by the corpus luteum, which produces
hormones until 10 to 14 days after ovulation
o Endometrium increases in size and readies for implantation
Uterine (Menstrual) Cycle

Secretory stage (continued)
o If fertilization does occur:
 Embryo produces a hormone that causes the corpus luteum to continue
producing its hormones
o If fertilization does NOT occur:
 Corpus luteum degenerates as LH blood levels decline
 The phases are repeated about every 28 days
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Hormone Production by the Ovaries

Estrogens are produced by follicle cells
o Cause secondary sex characteristics
 Enlargement of accessory organs of the female reproductive system
 Development of breasts
 Appearance of axillary and pubic hair
 Increase in fat beneath the skin, particularly in hips and breasts
 Widening and lightening of the pelvis
 Onset of menses (menstrual cycle)
Hormone Production by the Ovaries

Progesterone is produced by the corpus luteum
o Production continues until LH diminishes in the blood
o Does not contribute to the appearance of secondary sex characteristics
o Other major effects
 Helps maintain pregnancy
 Prepares the breasts for milk production
Mammary Glands



Present in both sexes, but function only in females
o Modified sweat glands
Function is to produce milk to nourish a newborn
Stimulated by sex hormones (mostly estrogens) to increase in size
Mammary Glands
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
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
Areola—central pigmented area
Nipple—protruding central area of areola
Lobes—internal structures that radiate around nipple
Lobules—located within each lobe and contain clusters of alveolar glands
Alveolar glands—produce milk when a woman is lactating (producing milk)
Lactiferous ducts—connect alveolar glands to nipple
Mammography



Mammography is X-ray examination that detects breast cancers too small to feel
Recommended every 2 years for women between 40 and 49 years old and yearly
thereafter
Breast cancer is often signaled by a change in skin texture, puckering, or leakage from
the nipple
Pregnancy and Embryonic Development


Pregnancy—time from fertilization until infant is born
Conceptus—developing offspring
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
o Embryo—period of time from fertilization until week 8
o Fetus—week 9 until birth
Gestation period—from date of last period until birth (approximately 280 days)
Accomplishing Fertilization




An oocyte is viable up to 24 hours after ovulation
Sperm are viable up to 48 hours after ejaculation
For fertilization to occur, sexual intercourse must occur no more than 2 days before
ovulation and no later than 24 hours after
Sperm cells must make their way to the uterine tube for fertilization to be possible
Accomplishing Fertilization



When sperm reach the oocyte, enzymes break down the follicle cells of the corona
radiata around the oocyte
Once a path is cleared, sperm undergo an acrosomal reaction (acrosomal
membranes break down, and enzymes digest holes in the oocyte membrane)
Membrane receptors on an oocyte pull in the head of the first sperm cell to make
contact
Accomplishing Fertilization



The membrane of the oocyte does not permit a second sperm head to enter
The oocyte then undergoes its second meiotic division to form the ovum and a polar
body
Fertilization occurs when the genetic material of a sperm combines with that of an
oocyte to form a zygote
Events of Embryonic & Fetal Development

Zygote
o First cell of a new individual
o The zygote is the result of the fusion of DNA from sperm and egg
o The zygote begins rapid mitotic cell divisions, known as cleavage, 24 hours
after fertilization
o The zygote journeys down the uterine tube, moving toward the uterus
Events of Embryonic & Fetal Development

Cleavage
o Rapid series of mitotic divisions that begins with the zygote and ends with the
blastocyst
o 3 to 4 days after ovulation, the preembryo reaches the uterus and floats freely
for 2 to 3 days
o Late blastocyst stage—embryo attaches to the endometrium (day 7 after
ovulation)
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o By day 14 after ovulation, implantation has occurred and the placenta is
forming
Events of Embryonic & Fetal Development


Embryo—period of time from fertilization until
week 8
o Morula—16-cell stage
o Blastocyst (chorionic vesicle)—hollow, ball-like structure containing about 100
cells
Fetus–week 9 until birth
Events of Embryonic & Fetal Development

Blastocyst (chorionic vesicle)
o Hollow, ball-like structure of 100 cells or more
o Secretes human chorionic gonadotropin (hCG) to induce the corpus luteum to
continue producing hormones, preventing menses, until the placenta assumes
its role
Events of Embryonic & Fetal Development

Functional areas of the blastocyst
1. Trophoblast—large fluid-filled sphere
2. Inner cell mass—cluster of cells to one side
Events of Embryonic & Fetal Development

Inner cell mass of blastocyst develops into:
o Primary germ layers
 Ectoderm—outside layer, which gives rise to nervous system and
epidermis of skin
 Endoderm—inside layer, which forms mucosae and associated glands
 Mesoderm—middle layer, which gives rise to everything else
Events of Embryonic & Fetal Development


After implantation, the trophoblast of the blastocyst develops chorionic villi
(projections)
o Chorionic villi combine with tissues of the uterus to form the placenta
Once the placenta has formed, the amnion is attached to the placenta by an umbilical
cord
o Amnion is a fluid-filled sac that surrounds the embryo
o Umbilical cord is a blood vessel–containing stalk of tissue
Events of Embryonic & Fetal Development
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
The placenta
o Forms a barrier between mother and embryo (blood is not exchanged)
o Delivers nutrients and oxygen
o Removes wastes from embryonic blood
o Becomes an endocrine organ and takes over for the corpus luteum (by end of
second month); produces estrogen, progesterone, and other hormones that
maintain pregnancy
Events of Embryonic & Fetal Development




All organ systems are formed by the end of the eighth week
Activities of the fetus are growth and organ specialization
The fetal stage is one of tremendous growth and change in appearance
Fetal changes are summarized in Table 16.1
Effects of Pregnancy on the Mother


Pregnancy—period from conception until birth
Anatomical changes
o Enlargement of the uterus
o Accentuated lumbar curvature (lordosis)
o Relaxation of the pelvic ligaments and pubic symphysis due to production of
relaxin
Effects of Pregnancy on the Mother

Physiological changes
o Gastrointestinal system
 Morning sickness is common and is due to elevated progesterone and
estrogens
 Heartburn is common because of organ crowding by the fetus
 Constipation is caused by declining motility of the digestive tract
Effects of Pregnancy on the Mother

Physiological changes (continued)
o Urinary system
 Kidneys have additional burden and produce more urine
 The uterus compresses the bladder, causing stress incontinence
Effects of Pregnancy on the Mother

Physiological changes (continued)
o Respiratory system
 Nasal mucosa becomes congested and swollen
 Vital capacity and respiratory rate increase
 Dyspnea (difficult breathing) occurs during later stages of pregnancy
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Effects of Pregnancy on the Mother

Physiological changes (continued)
o Cardiovascular system
 Blood volume increases by 25% to 40%
 Blood pressure and pulse increase
 Varicose veins are common
Childbirth (Parturition)

Initiation of labor
o Labor—the series of events that expel the infant from the uterus
 Rhythmic, expulsive contractions
 Operates by the positive feedback mechanism
o False labor—Braxton Hicks contractions are weak, irregular uterine
contractions
Childbirth (Parturition)

Initiation of labor
o Estrogen levels rise
o Uterine contractions begin
o The placenta releases prostaglandins
o Oxytocin is released by the pituitary
o Combined effects of rising levels of hormones, oxytocin and prostaglandins,
initiates contractions and forces the baby deeper into the mother’s pelvis
Stages of Labor

Dilation
o Cervix becomes dilated
o Full dilation is 10 cm
o Uterine contractions begin and increase
o Cervix softens and effaces (thins)
o The amnion ruptures (“breaking the water”)
o Longest stage at 6 to 12 hours
Stages of Labor

Expulsion
o Infant passes through the cervix and vagina
o Can last as long as 2 hours, but typically is 50 minutes in the first birth and 20
minutes in subsequent births
o Normal delivery is head-first (vertex position)
o Breech presentation is buttocks-first
Stages of Labor
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
Placental stage
o Delivery of the placenta
o Usually accomplished within 15 minutes after birth of infant
o Afterbirth—placenta and attached fetal membranes
o All placental fragments should be removed to avoid postpartum bleeding
Developmental Aspects of the Reproductive System




Gender is determined at fertilization
o Males have XY sex chromosomes
o Females have XX sex chromosomes
Reproductive system structures of males and females are identical during early
development
Gonads do not begin to form until the eighth week
The presence or absence of testosterone determines whether male or female
accessory reproductive organs will form
Developmental Aspects of the Reproductive System

Any interference with the normal pattern of sex hormone production in the embryo
results in abnormalities
o Pseudohermaphrodites are individuals whose external genitalia do not “match”
their gonads
o Hermaphrodites possess both ovarian and testicular tissues (rare)
Developmental Aspects of the Reproductive System

Important congenital defects result from abnormal separation of sex chromosomes
during sex cell formation
o Males who have an extra female sex chromosome have the normal male
accessory structures, but their testes atrophy, causing them to be sterile
o XO female lacks ovaries
o YO males die during development
Developmental Aspects of the Reproductive System



The reproductive system is inactive during childhood
Reproductive system organs do not function for childbearing until puberty
Puberty usually begins between ages 10 and 15
Developmental Aspects of the Reproductive System


Males
o Enlargement of testes and scrotum signals onset of puberty (often around age
13)
Females
o Budding breasts signal puberty (often around age 11)
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o Menarche—first menstrual period
Developmental Aspects of the Reproductive System



Common reproductive problems during young adulthood are infections of the
reproductive tract
Neoplasms of breast and cervix are major threats to women
Prostate cancer is the most common reproductive system cancer seen in men
Developmental Aspects of the Reproductive System


Menopause—a whole year has passed without menstruation
o Ovaries stop functioning as endocrine organs
o Childbearing ability ends
o Hot flashes and mood changes may occur
There is a no equivalent of menopause in males, but there is a steady decline in
testosterone
A Closer Look: Contraception


Contraception—birth control
Birth control pill—most-used contraceptive
o Relatively constant supply of ovarian hormones from pill is similar to pregnancy
o Ovarian follicles do not mature, ovulation ceases, menstrual flow is reduced
A Closer Look: Contraception


Morning-after pill (MAP)
o Taken within 3 days of unprotected intercourse
o Disrupts normal hormonal signals to the point that fertilization is prevented
Other hormonal birth control devices cause cervical mucus to thicken
o Minipill (tablet)
o Norplant (rods placed under the skin)
A Closer Look: Contraception


Intrauterine device (IUD)
o Plastic or metal device inserted into uterus
o Prevents implantation of fertilized egg
Sterilization
o Tubal ligation (females)—cut or cauterize uterine tubes
o Vasectomy (males)—cut or cauterize the ductus deferens
A Closer Look: Contraception


Coitus interruptus—withdrawal of penis prior to ejaculation
Rhythm (fertility awareness)—avoid intercourse during period of ovulation or fertility
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o Record daily basal temperature (body temperature rises after ovulation)
o Record changes in pattern of cervical mucus
A Closer Look: Contraception

Barrier methods
o Diaphragms
o Cervical caps
o Condoms
o Spermicidal foams
o Gels
o Sponges
A Closer Look: Contraception



Abortion—termination of pregnancy
Miscarriage—spontaneous abortion is common and frequently occurs before a
woman knows she is pregnant
RU486 or “abortion pill”—induces miscarriage during first 7 weeks of pregnancy
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