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Documents for "Anatomy and Physiology":
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abdomen
in humans and other vertebrates, portion of the trunk between the diaphragm and lower pelvis. In humans the wall of the abdomen is a muscular structure covered by fascia, fat, and skin. The...
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Achilles' tendon
( tendo calcaneus ) , sinew prominent at the back of the ankle, connecting the tendons of the calf muscles to the heelbone. When the musculature contracts, the pull on the Achilles' tendon elevates the heel in the...
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adenoids
common name for the pharyngeal tonsils, spongy masses of lymphoid tissue that occupy the nasopharynx, the space between the back of the nose and the throat. Normally the adenoids, like the...
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adrenal gland
or suprarenal gland , endocrine gland (see endocrine system ) about 2 in. (5.1 cm) long situated atop each kidney. The outer yellowish layer (cortex) of the adrenal gland secretes about 30 steroid hormones, the most important of which are aldosterone and cortisol. Cortisol regulates carbohydrate, protein, and fat metabolism, and its secretion is controlled by the output of adrenocorticotropic hormone (ACTH) from the pituitary gland. Aldosterone regulates water and salt balance in the body; its secretion is only slightly influenced by the pituitary. Steroid hormones also counteract inflammation...
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aging
in biology, cumulative changes in an organism, organ, tissue, or cell leading to a decrease in functional capacity. In humans, aging is associated with degenerative changes in the skin, bones,...
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anatomy
branch of biology concerned with the study of body structure of various organisms, including humans. Comparative anatomy is concerned with the structural differences of plant and animal forms. The...
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antibody
protein produced by the immune system (see immunity ) in response to the presence in the body of antigens: foreign proteins or polysaccharides such as bacteria, bacterial toxins , viruses, or other cells or proteins. Such antigens are capable of inflicting damage by chemically combining with natural substances in the body and disrupting the body's processes. The body...
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antitoxin
any of a group of antibodies formed in the body as a response to the introduction of poisonous products, or toxins. By introducing small amounts of a specific toxin into the healthy body, it is possible to stimulate the production of antitoxin so that the body's defenses are already established against invasion...
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aorta
primary artery of the circulatory system in mammals, delivering oxygenated blood to all other arteries except those of the lungs. The human aorta, c.1 in. (2.54 cm) in diameter, originates at the left ventricle of the heart. After supplying the coronary arteries that nourish the heart itself, the aorta extends slightly toward the neck to feed branches serving the head and arms. It then arches down toward the waist,...
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appendix
small, worm-shaped blind tube, about 3 in. (7.6 cm) long and 1/4 in. to 1 in. (.64-2.54 cm) thick, projecting from the cecum (part of the large intestine) on the right side of the lower abdominal cavity. The structure, also called the vermiform appendix, has no...
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arm
upper limb in humans. Three long bones form the framework of the arm: the humerus of the upper arm, and the radius (outer bone) and ulna (inner bone) of the forearm. The radius and ulna run...
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artery
blood vessel that conveys blood away from the heart. Except for the pulmonary artery, which carries deoxygenated blood from the heart to the lungs, arteries carry oxygenated blood from the heart to the tissues. The largest arterial trunk is the aorta , branches of which divide and subdivide into ever-smaller tubes, or arterioles, until they terminate as minute capillaries , the latter connecting with the veins (see circulatory system ). Other important arteries are the subclavian and brachial arteries of the shoulder and arm, the carotid arteries that lead to the head, the coronary arteries that nourish the heart itself, and the...
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axon
see nervous system ; synapse.
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biceps
any muscle having two heads, or fixed ends of attachment, notably the biceps brachii at the front of the upper arm and the biceps femoris in the thigh. Originating in the shoulder area, the heads...
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birth
or labor, delivery of the fetus by the viviparous mammal. Birth is also known as parturition. Human birth normally occurs about 280 days after onset of the last menstrual period before conception.
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bladder, urinary
muscular sac located in the pelvis that stores urine and contracts to expel it from the body. Urine enters the bladder from the kidneys through the ureters and is discharged from the body via the urethra. The bladder of the adult human can hold over a pint (0.6 liters) of urine. When the level of urine reaches about half this amount, pressure of the accumulating fluid stimulates nervous impulses...
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blood
fluid pumped by the heart that circulates throughout the body via the arteries, veins, and capillaries (see circulatory system ; heart ). An adult male of average size normally has about 6 quarts (5.6 liters) of blood. The blood carries oxygen and nutrients to the body tissues and removes carbon dioxide and other wastes. The...
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blood clotting
process by which the blood coagulates to form solid masses, or clots. In minor injuries, small oval bodies called platelets, or thrombocytes, tend to collect and form plugs in blood vessel...
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blood groups
differentiation of blood by type, classified according to immunological (antigenic) properties, which are determined by specific substances on the surface of red blood cells. Blood groups are...
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blood pressure
force exerted by the blood upon the walls of the arteries. The pressure in the arteries originates in the pumping action of the heart, and pressure waves can be felt at the wrist and at other...
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body temperature
internal temperature of a living organism. Mammals and birds are termed warm-blooded, or homeothermic, i.e., they are able to maintain a relatively constant inner body temperature, whereas other...
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bone
hard tissue that forms the skeleton of the body in vertebrate animals. In the very young, the skeleton is composed largely of cartilage and is therefore pliable, reducing the incidence of bone fracture and breakage in childhood. The...
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bone marrow
soft tissue filling the spongy interiors of animal bones. Red marrow is the principal organ that forms blood cells in mammals, including humans (see blood ). In children, the bones contain only red marrow. As the skeleton matures, fat-storing yellow marrow displaces red marrow in the shafts of the long bones of the limbs. In adults red marrow remains...
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brain
the supervisory center of the nervous system in all vertebrates. It also serves as the site of emotions, memory, self-awareness, and thought.
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brain stem
lower part of the brain , adjoining and structurally continuous with the spinal cord. The upper segment of the human brain stem, the pons, contains nerve fibers that connect the two halves of the cerebellum. It is vital in coordinating movements involving right and left sides of the body. Below the pons and continuous with the spinal cord is the medulla, which transmits ascending and descending nerve...
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bursa
closed fibrous sac lined with a smooth membrane, producing a viscous lubricant known as synovial fluid. Bursas are found in regions where muscles or tendons rub against other muscles, tendons, or...
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capillary
microscopic blood vessel, smallest unit of the circulatory system. Capillaries form a network of tiny tubes throughout the body, connecting arterioles (smallest arteries ) and venules (smallest veins ). Through the thin capillary walls, which are composed of a single layer of cells, the nutritive material and oxygen in the blood pass into the body tissues, and waste matter and carbon dioxide in...
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cartilage
flexible semiopaque connective tissue without blood vessels or nerve cells. It forms part of the skeletal system in humans and in other vertebrates, and is also known as gristle. Temporary cartilage makes up the skeletal system of the...
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