Glossary 549ticoid) secreted by the adrenal cortex that increases the
reabsorption of sodium and the excretion of potassium by
the kidneys (Chapter 10).
Alimentary tube(AL-i-MEN-tah-ree TOOB) The series
of digestive organs that extends from the mouth to the
anus; consists of the oral cavity, pharynx, esophagus,
stomach, small intestine, and large intestine (Chapter 16).
Allele(uh-LEEL) One of two or more different genes for a
particular characteristic (Chapter 21).
Allergen(AL-er-jen) A substance capable of stimulating an
allergic response (Chapter 14).
Allergy(AL-er-jee) A hypersensitivity to a foreign antigen
that usually does not stimulate an immune response in
people; the immune response serves no useful purpose
(Chapter 14).
Alopecia(AL-oh-PEE-she-ah) Loss of hair, especially that
of the scalp (Chapter 5).
Alpha cells(AL-fah SELLS) The cells of the islets of
Langerhans of the pancreas that secrete the hormone
glucagon (Chapter 10).
Alveolar type I cell(al-VEE-oh-lar TIGHP WON SELL)
The simple squamous epithelial cell that forms the walls
of the alveoli of the lungs (Chapter 15).
Alveolar type II cell(al-VEE-oh-lar TIGHP TOO SELL)
The septal cell in the lungs that produces pulmonary sur-
factant (Chapter 15).
Alveolar ventilation(al-VEE-oh-lar VEN-ti-LAY-shun)
The amount of inhaled air that reaches the alveoli and
participates in gas exchange; about 350–400 mL of a 500-
mL tidal volume (Chapter 15).
Alveoli(al-VEE-oh-lye) The air sacs of the lungs, made of
simple squamous epithelium, in which gas exchange takes
place (Chapter 15).
Alzheimer’s disease(ALZ-high-mers) A progressive brain
disease, of unknown cause, resulting in loss of memory,
intellectual ability, speech, and motor control (Chap-
ter 8).
Amblyopia(AM-blee-OH-pee-ah) Impaired vision without
apparent damage to an eye; often the result of lazy eye
because the brain ignores the image from the lazy eye
and the eye stops focusing (Chapter 9).
Amenorrhea(ay-MEN-uh-REE-ah) Absence of menstrua-
tion (Chapter 20).
Amine/amino group(ah-MEEN/ah-MEE-noh) The NH 2
portion of a molecule such as an amino acid (Chapter 12).
Amino acid(ah-MEE-noh ASS-id) An organic compound
that contains an amino, or amine, group (NH 2 ) and a
carboxyl group (COOH). Twenty different amino acids
are the subunit molecules of which human proteins are
made (Chapter 2).
Amniocentesis (AM-nee-oh-sen-TEE-sis) A diagnostic
procedure in which amniotic fluid is obtained for culture
of fetal cells; used to detect genetic diseases or other
abnormalities in the fetus (Chapter 21).Amnion(AM-nee-on) An embryonic membrane that holds
the fetus suspended in amniotic fluid; fuses with the
chorion by the end of the third month of gestation
(Chapter 21).
Amniotic fluid(AM-nee-AH-tik FLOO-id) The fluid con-
tained within the amnion; cushions the fetus and absorbs
shock (Chapter 21).
Amphiarthrosis(AM-fee-ar-THROH-sis) A slightly mov-
able joint, such as a symphysis (Chapter 6).
Amylase(AM-i-lays) A digestive enzyme that breaks down
starch to maltose; secreted by the salivary glands and the
pancreas (Chapter 16).
Anabolic steroid(AN-ah-BAH-lik STEER-oyd) A chemi-
cal similar in structure and action to the male hormone
testosterone; increases protein synthesis, especially in
muscles (Chapter 7).
Anabolism(an-AB-uh-lizm) Synthesis reactions, in which
smaller molecules are bonded together to form larger
molecules; require energy (ATP) and are catalyzed by
enzymes (Chapter 17).
Anaerobic(AN-air-ROH-bik) 1. In the absence of oxygen.- Not requiring oxygen (Chapter 7).
Anaphase(AN-ah-fayz) The third stage of mitosis, in which
the separate sets of chromosomes move toward opposite
poles of the cell (Chapter 3).
Anaphylactic shock(AN-uh-fi-LAK-tik SHAHK) A type
of circulatory shock that is the result of a massive allergic
reaction (from the Greek “unguarded”) (Chapter 13).
Anastomosis(a-NAS-ti-MOH-sis) A connection or join-
ing, especially of blood vessels (Chapter 13).
Anatomic position (AN-uh-TOM-ik pa-ZI-shun) The
position of the body used in anatomic descriptions: The
body is erect and facing forward, the arms are at the sides
with the palms facing forward (Chapter 1).
Anatomy(uh-NAT-uh-mee) The study of the structure
of the body and the relationships among the parts
(Chapter 1).
Anemia(uh-NEE-mee-yah) A deficiency of red blood cells
or hemoglobin (Chapter 11).
Anencephaly(an-en-SEFF-ah-lee) A congenital nervous
system defect in which the cerebrum has not developed;
is always fatal (Chapter 17).
Aneurysm(AN-yur-izm) A localized sac or bubble that
forms in a weak spot in the wall of a blood vessel, usually
an artery (Chapter 13).
Angiotensin II(AN-jee-oh-TEN-sin 2) The final product
of the renin-angiotensin mechanism; stimulates vasocon-
striction and increased secretion of aldosterone, both of
which help raise blood pressure (Chapter 13).
Anion(AN-eye-on) An ion with a negative charge (Chapter
2).
Antagonistic muscles(an-TAG-on-ISS-tik MUSS-uhls)
Muscles that have opposite functions with respect to the
movement of a joint (Chapter 7).
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