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The Human Body—An Orientation Anatomy Study of the structure and shape of the body and its parts Observation is used to see sizes and relationships of parts Anatomy—Levels of Study Gross anatomy o Large structures o Easily observable The Human Body—An Orientation Let’s look at an example of gross anatomy using the digestive system organs Anatomy—Levels of Study 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 Study of how the body and its parts work or function Relationship between Anatomy and Physiology Structure determines what functions can occur If structure changes, the function must also change Levels of Structural Organization Six levels of structural organization 1. Atoms 2. Cells 3. Tissues 4. Organs 5. Organ systems 6. Organisms Organ System Overview Integumentary system o Forms the external body covering (skin) © 2015Pearson Education, Inc. o Protects deeper tissue from injury o Helps regulate body temperature o Location of cutaneous nerve receptors Organ System Overview 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 Muscular system o Skeletal muscles contract or shorten o Produces movement of bones Organ System Overview 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 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 Endocrine system o Secretes regulatory hormones Growth Reproduction Metabolism © 2015Pearson Education, Inc. Organ System Overview 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 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 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 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 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 Reproductive system o For males, includes the testes, scrotum, penis, accessory glands, and duct system © 2015Pearson Education, Inc. 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 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 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 Reproduction o Occurs on cellular level or organismal level o Produces future generation Growth o Increases cell size and number of cells Survival Needs Nutrients o Chemicals for energy and cell building o Includes carbohydrates, proteins, lipids, vitamins, and minerals Oxygen o Required for chemical reactions Survival Needs © 2015Pearson Education, Inc. Water 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 Homeostasis 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 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 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 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 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 © 2015Pearson Education, Inc. a baby The Language of Anatomy Special terminology is used to prevent misunderstanding Exact terms are used for: o Position o Direction o Regions o Structures The Language of Anatomy 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 Directional terms o Explains location of one body structure in relation to another Directional Terms 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 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 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 Proximal: close to the origin of the body part or point of attachment to a limb to the body trunk © 2015Pearson Education, Inc. Distal: farther from the origin of a body part or the point of attachment of a limb to the body trunk Directional Terms Superficial (external): toward or at the body surface Deep (internal): away from the body surface; more internal Regional Terms Anterior (ventral) body landmarks Regional Terms Posterior (dorsal) body landmarks Body Planes and Sections 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 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 Two body cavities o Dorsal o Ventral Body cavities provide varying degrees of protection to organs within them Body Cavities 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 © 2015Pearson Education, Inc. Body Cavities Ventral body cavity has two subdivisions separated by the diaphragm 1. Thoracic cavity 2. Abdominopelvic cavity Body Cavities 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 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 Abdominopelvic cavity subdivisions o Four quadrants o Nine regions Body Cavities Other body cavities include: o Oral and digestive cavities o Nasal cavity o Orbital cavities o Middle ear cavities © 2015Pearson Education, Inc. Matter and Energy 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 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 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 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 Energy form conversions o ATP (adenosine triphosphate) traps the chemical energy of food in its bonds Composition of Matter 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 © 2015 Pearson Education, Inc. Composition of Matter Atoms o o o o 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 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 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 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 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 Electrons determine an atom’s chemical behavior Although outdated, the planetary model is simple and easy to understand and use Identifying Elements Atomic number—equal to the number of protons that the atom contains o Unique to atoms of a particular element © 2015 Pearson Education, Inc. 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 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 Atomic weight o Close to mass number of most abundant isotope o Atomic weight reflects natural isotope variation Radioactivity 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 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 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 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 © 2015 Pearson Education, Inc. Electrons and Bonding 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 Bonding involves only interactions between electrons in the outer (valence) shell Atoms with full valence shells do not form bonds Inert Elements 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 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 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 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 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 © 2015 Pearson Education, Inc. Chemical Bonds 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 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 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 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 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 Exchange reaction (AB + C → AC + B and AB + CD → AD + CB) © 2015 Pearson Education, Inc. 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 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 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 Water o Most abundant inorganic compound in the body o Vital properties High heat capacity Polarity/solvent properties Chemical reactivity Cushioning Important Inorganic Compounds 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 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 © 2015 Pearson Education, Inc. o Colloid forms when solutes of intermediate size form a translucent mixture Important Inorganic Compounds 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 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 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 Salts o All salts are electrolytes o Electrolytes are ions that conduct electrical currents Important Inorganic Compounds Acids o o o o o 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 Bases o Release hydroxyl ions (OH–) when dissolved in water o Are proton acceptors o Example: NaOH → Na+ + OH– © 2015 Pearson Education, Inc. o Strong bases seek hydrogen ions Important Inorganic Compounds 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 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 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 Polymer: chainlike molecules made of many similar or repeating units (monomers) Many biological molecules are polymers, such as carbohydrates and proteins Chemical Reactions 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 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 © 2015 Pearson Education, Inc. 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 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 Disaccharides—two simple sugars joined by dehydration synthesis o Examples include sucrose, lactose, and maltose Carbohydrates 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 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 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 © 2015 Pearson Education, Inc. Lipids 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 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 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 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 Proteins o Account for over half of the body’s organic matter © 2015 Pearson Education, Inc. 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 Amino acid structure o Contain an amine group (NH2) o Contain an acid group (COOH) o Vary only by R groups Proteins 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 Structural levels of proteins o Primary structure o Secondary structure Alpha helix Beta-pleated sheet o Tertiary structure o Quaternary structure Proteins 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 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 © 2015 Pearson Education, Inc. Enzymes 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 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 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 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 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 © 2015 Pearson Education, Inc. Nucleic Acids 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 ADP (adenosine diphosphate) accumulates as ATP is used for energy Three examples of how ATP drives cellular work are shown next © 2015 Pearson Education, Inc. Cells 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 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 In general, a cell has three main regions or parts: 1. Nucleus 2. Cytoplasm 3. Plasma membrane The Nucleus 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 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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) © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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. © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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) © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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) © 2015 Pearson Education, Inc. 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) © 2015 Pearson Education, Inc. 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) © 2015 Pearson Education, Inc. 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, © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 Cerebral hemispheres (cerebrum) Diencephalon Brain stem Cerebellum Regions of the Brain: Cerebrum 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 © 2015 Pearson Education, Inc. 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 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 Sits on top of the brain stem Enclosed by the cerebral hemispheres Made of three parts: 1. Thalamus 2. Hypothalamus 3. Epithalamus © 2015 Pearson Education, Inc. 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 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 © 2015 Pearson Education, Inc. 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 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 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 © 2015 Pearson Education, Inc. o Folds inward in several areas Falx cerebri Tentorium cerebelli Meninges 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) 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 © 2015 Pearson Education, Inc. Blood-Brain Barrier 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. o Maintains daily necessary body functions o Remember as the “D” division Digestion Defecation Diuresis Developmental Aspects of the Nervous System 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. © 2015 Pearson Education, Inc. The Senses Special senses o Smell o Taste o Sight o Hearing o Equilibrium The Eye and Vision 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 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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) © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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) © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. Leukemias are most common in the very young and very old o Older adults are also at risk for anemia and clotting disorders © 2015 Pearson Education, Inc. 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: © 2015 Pearson Education, Inc. 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”) © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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: © 2015 Pearson Education, Inc. 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): © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. chronic hypoxia Respiratory Disorders: Emphysema 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) © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. The Digestive System Functions 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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) © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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) © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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) © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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: © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. Oogenesis and the Ovarian Cycle 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 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 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 © 2015 Pearson Education, Inc. 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) © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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) © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc. 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 © 2015 Pearson Education, Inc.