Download Chapter 7: Anatomy and Physiology

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• To care for your patients properly, you must have a thorough understanding of human
anatomy and physiology so you can assess the patient’s condition and communicate with
hospital personnel and other health care providers.
• You must be able to identify superficial landmarks of the body and know what lies
underneath the skin so that you can perform an accurate patient assessment.
• If you understand the basics of chemistry, your understanding of anatomy and physiology
will be improved. Chemical changes within cells influence body functions and the status of
the body’s structures.
• Chemicals can basically be divided into two main groups: organic and inorganic. Organic
substances include carbohydrates, lipids, proteins, and nucleic acids. Inorganic substances
in body cells include oxygen, carbon dioxide, compounds that are known as salts, and
water.
• Cells are the foundation of the human body. Cells with a common job grow close to each
other and are called tissues. Groups of tissues that all perform interrelated jobs form organs.
• Cell transport mechanisms, or how materials enter and exit cells, relates to fluid
administration. Several mechanisms, such as diffusion, osmosis, facilitated diffusion, active
transport, endocytosis, and exocytosis allow material to pass through the cell wall.
• The cell’s life cycle is regulated via stimulation from hormones or growth factors. The life
of a cell includes interphase, cell division or mitosis, cytoplasmic division, and
differentiation.
• The human body is primarily made up of four major types of tissue: epithelial, connective,
muscle, and nervous tissues.
• Membranes form a barrier or an interface. The four types of membranes are serous
membranes, mucous membranes, cutaneous membranes, and synovial membranes.
• Organs systems include the integumentary, skeletal, muscular, nervous, endocrine,
cardiovascular, lymphatic, digestive, respiratory, urinary, and reproductive systems.
• The skeleton gives the body its recognizable human form through a collection of bones,
ligaments, tendons, and cartilage.
• Bones are classified according to their shape, as long bones, short bones, flat bones, and
irregular bones. The bones increase greatly in size as the fetus develops and throughout
adolescence.
• Joints are classified as immovable (synarthrotic), slightly moveable (amphiarthrotic), or
freely movable (diarthrotic). Most joints allow motion (knee, hip, elbow), and some bones
fuse with one another at joints to form a solid, immobile, bony structure (skull).
• The 230 joints in the human body are fibrous, cartilaginous, or synovial.
• The human body contains several cavities that can be grouped into dorsal cavities
(posterior) and ventral cavities (anterior).
• The axial skeleton forms the foundation on which the arms and legs are hung. The arms and
legs, their connection points, and the pelvis make up the appendicular skeleton.
• The skeletal system is responsible for several functions. Bones protect internal organs and
muscles enable movement. Bone also serves as a storage site for minerals, particularly
calcium, and has a role in the formation of blood cells and platelets.
• Smooth muscle is found within blood vessels and intestines, and controls involuntary
functions. Skeletal muscle, so named because it attaches to the bones of the skeleton, forms
the major muscle mass of the body. It is also called voluntary muscle, because all skeletal
muscle is under direct voluntary control.
• The contraction and relaxation of the musculoskeletal system gives the body its ability to
move. Skeletal muscles contract when organelles and molecules bind myosin to actin to
cause a pulling action.
• Cardiac muscle is different from skeletal and smooth muscle because it has the property of
“automaticity”; it can generate and conduct electricity without influence from the brain.
• The respiratory system consists of all the structures of the body that contribute to the
process of breathing. It includes the nose, mouth, throat, larynx, trachea, bronchi, and
bronchioles. The system also includes the lungs, diaphragm, the muscles of the chest wall,
and the accessory muscles of breathing.
• The primary function of the respiratory system is to conduct respiration. Oxygen is essential
for the body to function. Gas exchange of oxygen into the blood and carbon dioxide out of
the blood occurs at the alveoli of the lungs via diffusion.
• The respiratory center in the brainstem controls breathing. Nerves in this area sense the
level of carbon dioxide in the blood and spinal fluid. The brain adjusts breathing as needed
if the level of carbon dioxide or oxygen in the arterial blood is too high or too low.
• Increases in the level of carbon dioxide in the blood (PaCO2) cause decreased pH levels in
the respiratory center, which triggers an increase in ventilation. Decreases in the PaCO2
result in increased pH levels in the respiratory center and a decrease in ventilation.
• Hypoxic drive is a backup system the body uses to control respiration. Areas in the brain,
walls of the aorta, and carotid arteries act as oxygen sensors and stimulate breathing if the
oxygen level falls.
• The medulla oblongata is primarily responsible for initiating the ventilation cycle and is
primarily stimulated by high carbon dioxide levels.
• The medulla has two main portions that control breathing: the dorsal respiratory group
(DRG) and the ventral respiratory group (VRG). The DRG is the main pacemaker for
breathing and is responsible for initiating inspiration. The VRG helps to provide for forced
inspiration or expiration as needed.
• The circulatory system is a complex arrangement of connected tubes, including the arteries,
arterioles, capillaries, venules, and veins.
• The cardiac cycle begins with myocardial contraction and concludes at the beginning of the
next contraction. The heart’s contraction results in pressure changes within the cardiac
chambers, resulting in the movement of blood from areas of high pressure to areas of low
pressure.
• The pressure in the aorta against which the left ventricle must pump blood is called the
afterload. The greater the afterload, the harder it is for the ventricle to eject blood into the
aorta. This reduces the stroke volume—the amount of blood ejected per contraction.
• Cardiac output is the amount of blood pumped through the circulatory system in 1 minute.
Cardiac output is expressed in liters per minute (L/min). The cardiac output equals the heart
rate multiplied by the stroke volume.
• Increased venous return to the heart stretches the ventricles, resulting in increased cardiac
contractility. This relationship is known as the Frank-Starling mechanism.
• Blood consists of plasma and formed elements or cells that are suspended in the plasma.
These cells include red blood cells, white blood cells, and platelets.
• Blood has many functions including fighting infection, transporting oxygen and carbon
dioxide, controlling pH, transporting wastes and nutrients, and clotting.
• The lymphatic system helps absorb fat from the digestive tract, maintain fluid balance in the
body, and fight infection. The spleen is the body’s largest lymphatic organ.
• Body defenses can be divided into two general categories: innate (nonspecific) and adaptive
(specific) defenses. Immunity is known as the third line of defense.
• The nervous system is perhaps the most complex organ system within the human body. It
consists of the brain, spinal cord, and nerves.
• The nervous system is responsible for fundamental functions such as controlling breathing,
heart rate, and blood pressure. This system also allows the performance of higher level
activity, such as memory, understanding, and thought.
• The nervous system is divided into the central nervous system (CNS) and the peripheral
nervous system. The CNS includes the brain and the spinal cord. The somatic nervous
system is the part of the peripheral nervous system that regulates activities over which there
is voluntary control, such as walking, talking, and writing. The autonomic nervous system
is the part of the peripheral nervous system that controls the many body functions that occur
without voluntary control such as digestion, dilation and constriction of blood vessels, and
sweating.
• The autonomic nervous system is split into two areas. The sympathetic nervous system is
responsible for fight-or-flight response, and the parasympathetic nervous system is
responsible for moving blood to the stomach and intestines after eating and for many
reproductive functions.
• There are two types of nerves within the peripheral nervous system, sensory nerves and
motor nerves.
• The integumentary system is the skin. The skin is divided into two parts: the superficial
epidermis, which is composed of several layers of cells including the germinal layer and the
stratum corneal layer, and the deeper dermis, which contains the specialized skin structures
such as sweat glands, sebaceous (oil) glands, nails, hair follicles, blood vessels, and
specialized nerve endings.
• Subcutaneous tissue is below the skin and is composed largely of fat, serving as an insulator
for the body and as a reservoir to store energy. The subcutaneous layer also helps to anchor
the skin to the structures beneath it.
• The skin, the largest single organ in the body, serves three major functions: to protect the
body in the environment, to regulate the temperature of the body, and to transmit
information from the environment to the brain.
• The functions of the digestive system consist of a series of steps, which include ingestion,
mechanical processing, digestion, secretion, absorption, and excretion.
• The alimentary canal extends from the mouth to the anus. It includes the mouth, pharynx,
esophagus, stomach, small intestine, large intestine, rectum, and anus. The accessory organs
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of the alimentary canal include the teeth, tongue, salivary glands, liver, gallbladder, and
pancreas.
The endocrine system is made up of various glands located throughout the body.
Endocrine glands help regulate metabolism, control chemical reactions, transport
substances, regulate water and electrolyte balances, and aid in reproduction, growth, and
development.
The major endocrine glands include the pituitary gland, thyroid gland, parathyroid glands,
adrenal glands, pancreas, pineal gland, thymus gland, and reproductive glands.
The main functions of the urinary system are to control fluid balance in the body, to filter
and eliminate wastes, and to control pH balance.
In the urinary system, the kidneys are solid organs; the ureters, bladder, and urethra are
hollow organs.
The kidneys rid the blood of toxic waste products and control its balance of water and salt.
The total body water content of the average adult ranges from 50% to 70% of total body
weight, depending on age and sex.
Body fluid is divided into intracellular and extracellular fluid compartments. Intracellular
fluid exists within individual cells and makes up approximately 75% of all body fluid.
Extracellular fluid exists outside of the cell membranes. The body can maintain fluid
balance by shifting water from one compartment to another.
The reproductive systems of both males and females contain organs and glands that create
sex cells and transport them to areas where fertilization can occur.
Chromosomes contain the entire sequence of genetic information the organism will have
throughout its entire life. This genetic information contains the instructions for every
structure and process in the body. They also contain sequences that will determine or
influence various characteristics such as hair color, skin color, body composition, height,
and predisposition to certain diseases.
The primary sex organs (gonads) of the male consist of the two testes, in which sperm cells
and male sex hormones are formed.
Male reproductive functions are controlled by hormones from the hypothalamus, anterior
pituitary gland, and testes.
Testosterone enlarges the testes and accessory reproductive organs, and develops the male
secondary sex characteristics. These characteristics include increased amount of body hair;
enlargement of the larynx and thickening of vocal folds, which lowers the pitch of the
voice; thickening of the skin; increased muscular growth; and thickening and strengthening
of bones.
The female reproductive organs produce and maintain the oocytes, which are the female sex
cells.
The primary sex organs (gonads) of the female are the two ovaries, which reproduce female
sex cells and sex hormones.
The hypothalamus, anterior pituitary gland, and ovaries control the maturation of female
sex cells, development and maintenance of secondary sex characteristics, and changes
during the monthly reproductive cycle.
In nonpregnant females, the ovaries are the main source of estrogens, and they secrete
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increasing amounts of estrogens beginning at puberty. These hormones stimulate
enlargement of accessory sex organs and develop and maintain the female secondary sex
characteristics including development of breasts and mammary gland systems.
The female reproductive cycle involves regular, recurring changes in the uterine lining as
well as menstrual bleeding (menses).
The body obtains most nutrients through ingestion (food) and inhalation (oxygen).
Nutrients include carbohydrates, lipids, proteins, vitamins, minerals, and water.
Digestion breaks down nutrients so they can be absorbed and transported via the
bloodstream.
Individual cells are supplied the nutrients and use them in various processes. As a result of
cellular metabolism, organisms grow, maintain body functions, release or store energy,
produce and eliminate waste, digest nutrients, or destroy toxins. These reactions alter the
chemical nature of a chemical substance, maintaining homeostasis.
In the body, enzymes assist in the digestion of food, drug metabolism, protein formation,
and many other types of reactions.
Cellular respiration is a process that releases energy from organic compounds. This process
requires three types of reactions: glycolysis, the citric acid cycle, and the electron transport
chain.
Heat is a by-product of many cellular and chemical processes; the presence of body heat is
one of the most basic signs of life.
Body temperature regulation begins in the hypothalamus, which acts similar to a thermostat
in activating the mechanisms for increasing or decreasing body temperature.