548 Glossaryteeth, tongue, salivary glands, liver, gallbladder, and pan-
creas (Chapter 16).
Acetabulum(ASS-uh-TAB-yoo-lum) The deep socket in
the hip bone that articulates with the head of the femur
(from the Latin “little vinegar cup”) (Chapter 6).
Acetylcholine(as-SEE-tull-KOH-leen) A chemical neuro-
transmitter released at neuromuscular junctions, as well
as by neurons in the central and peripheral nervous sys-
tems (Chapter 7).
Acid(ASS-id) A hydrogen ion (H) donor; when in solution
has a pH less than 7 (Chapter 2).
Acidosis(ASS-i-DOH-sis) The condition in which the pH
of the blood falls below 7.35 (Chapter 2).
Acne(AK-nee) Inflammation of the sebaceous glands and
hair follicles (Chapter 5).
Acoustic nerves(uh-KOO-stik) Cranial nerve pair VIII.
Sensory for hearing and equilibrium (Chapter 8).
Acquired immunity (uh-KWHY-erd im-YOO-ni-tee)
The immunity obtained upon exposure to a pathogen or
a vaccine or upon reception of antibodies for a particular
pathogen (Chapter 14).
Acromegaly (AK-roh-MEG-ah-lee) Hypersecretion of
growth hormone in an adult, resulting in exces-
sive growth of the bones of the face, hands, and feet
(Chapter 10).
Acrosome(AK-roh-sohm) The tip of the head of a sperm
cell, a modified lysosome; contains enzymes to digest the
membrane of the ovum (Chapter 20).
Actin(AK-tin) A contractile protein in the sarcomeres of
muscle fibers; is pulled by myosin (Chapter 7).
Action potential(AK-shun poh-TEN-shul) The changes
in electrical charges on either side of a cell membrane in
response to a stimulus; depolarization followed by repo-
larization (Chapter 7).
Active immunity(AK-tiv im-YOO-ni-tee) The immunity
provided by the production of antibodies after exposure
to a foreign antigen; may be natural (recovery from dis-
ease) or artificial (reception of a vaccine) (Chapter 14).
Active site theory (AK-tiv SITE THEER-ree) The
process by which an enzyme catalyzes a specific reaction;
depends on the shapes of the enzyme and the substrate
molecules (Chapter 2).
Active transport(AK-tiv TRANS-port) The process in
which there is movement of molecules against a concen-
tration gradient; that is, from an area of lesser concentra-
tion to an area of greater concentration. Requires energy
(Chapter 3).
Acute(ah-KEWT) 1. Characterized by rapid onset. 2.
Sharp or severe, with respect to symptoms; not chronic.
(Chapter 22).
Adaptation(A-dap-TAY-shun) The characteristic of sensa-
tions in which awareness of the sensation diminishes
despite a continuing stimulus (Chapter 9).
Addison’s disease(ADD-i-sonz) Hyposecretion of the hor-mones of the adrenal cortex, characterized by low blood
pressure, dehydration, muscle weakness, and mental
lethargy (Chapter 10).
Adduction(ad-DUK-shun) The movement of a body part
toward the midline of the body (Chapter 7).
Adenohypophysis (uh-DEN-oh-high-POFF-e-sis) The
anterior pituitary gland (Chapter 10).
Adipocyte(ADD-i-poh-site) A cell of adipose tissue, spe-
cialized to store fat (Chapter 4).
Adipose tissue(ADD-i-pohz TISH-yoo) A connective tis-
sue composed primarily of adipocytes; function is fat
storage as a source of potential energy (Chapter 4).
Adrenal cortex(uh-DREE-nuhl KOR-teks) The outer
layer of the adrenal glands, which secretes cortisol and
aldosterone (Chapter 10).
Adrenal glands(uh-DREE-nuhl) The endocrine glands
located on the top of the kidneys; each consists of
an adrenal cortex, which secretes cortisol and aldos-
terone, and an adrenal medulla, which secretes epineph-
rine and norepinephrine (Syn.—suprarenal glands)
(Chapter 10).
Adrenal medulla(uh-DREE-nuhl muh-DEW-lah) The
inner layer of the adrenal glands; secretes epinephrine
and norepinephrine (Chapter 10).
Adrenocorticotropic hormone(ACTH) (uh-DREE-no-
KOR-ti-koh-TROH-pik) A hormone produced by the
anterior pituitary gland that stimulates the adrenal cortex
to secrete cortisol (Chapter 10).
Aerobic(air-ROH-bik) Requiring oxygen (Chapter 3).
Afferent(AFF-er-rent) To carry toward a center or main
part (Chapter 8).
Afferent arteriole(AFF-er-ent ar-TIR-ee-ohl) The arteri-
ole that takes blood from the renal artery into a glomeru-
lus; within its wall are juxtaglomerular cells that secrete
renin (Chapter 18).
Afterbirth(AFF-ter-berth) The placenta delivered shortly
after delivery of the infant (Chapter 21).
After-image(AFF-ter-IM-ije) The characteristic of sensa-
tions in which a sensation remains in the consciousness
even after the stimulus has stopped (Chapter 9).
Age-related macular degeneration(AMD) (MAK-yoo-
lar dee-jen-e-RAY-shun) Loss of central vision because
of the growth of abnormal blood vessels or bleeding in
the retina (Chapter 9).
Agglutination (uh-GLOO-ti-NAY-shun) Clumping of
blood cells or microorganisms; the result of an anti-
gen–antibody reaction (Chapter 11).
AIDS(AYDS) Acquired immunodeficiency syndrome;
caused by a virus (HIV) that infects helper T cells and
depresses immune responses (Chapter 14).
Albumin(al-BYOO-min) A protein synthesized by the
liver, which circulates in blood plasma; contributes to the
colloid osmotic pressure of the blood (Chapter 11).
Aldosterone(al-DAH-ster-ohn) A hormone (mineralocor-30Scanlon(p3) Glossary 8/17/06 11:08 AM Page 548