Glossary
G-2
adenylate cyclase
(ad ′ e-nil- ā te s ī kl ā s) An en-zyme acting on ATP to form 3 ′ ,5 ′ -cyclic AMPplus pyrophosphate (two phosphate groups). Acrucial step in the regulation and formation ofthe intracellular chemical signal 3 ′ ,5 ′ -cyclicAMP.
adipocyte
(ad ′ i-p ō -s ī t) Fat cell.
adipose
(ad ′ i-p ō s) [L.,
adeps,
fat] Fat.
adrenal gland
( ă -dr ē ′ n ă l) [L.,
ad,
to +
ren,
kidney]Located near the superior pole of each kidney, it iscomposed of a cortex and a medulla. The adrenalmedulla is a highly modified sympathetic gan-glion that secretes the hormones epinephrine andnorepinephrine; the cortex secretes aldosteroneand cortisol as its major secretory products. Alsocalled suprarenal gland.
adrenergic neuron
(ad-r ĕ -ner ′ jik) Nerve fiber thatsecretes norepinephrine (or epinephrine) as aneurotransmitter substance.
adrenergic receptor
(ad-r ĕ -ner ′ jik) Receptor mol-ecule that binds to adrenergic agents, such asepinephrine and norepinephrine.
adrenocorticotropic hormone (ACTH)
( ă -dr ē ′ n ō -k ō r ′ ti-k ō -tr ō ′ pik) Hormone of the adenohy-pophysis that governs the nutrition and growthof the adrenal cortex, stimulates it to functionalactivity, and causes it to secrete cortisol.
adventitia
(ad-ven-tish ′ ă ) [L.,
adventicius,
com-ing from abroad, foreign] Outermost covering ofany organ or structure that is properly derivedfrom outside the organ and does not form an in-tegral part of the organ.
aerobic respiration
( ā r- ō ′ bik) Breakdown of glu-cose in the presence of oxygen to producecarbon dioxide, water, and approximately 38ATPs; includes glycolysis, the citric acid cycle,and the electron-transport chain.
afferent arteriole
(af ′ er-ent) Branch of an inter-lobular artery of the kidney that conveys bloodto the glomerulus.
afferent division
Nerve fibers that send impulsesfrom the periphery to the central nervous system.
agglutination
( ă -gloo-ti-n ā -sh ŭ n) [L.,
ad,
to +
gluten,
glue] Process by which blood cells, bacteria, orother particles are caused to adhere to one anotherand form clumps.
agglutinin
( ă -gloo ′ ti-nin) Antibody that binds toan antigen and causes agglutination.
agglutinogen
( ă -gloo-tin ′ ō -jen) Antigen on surfaceof red blood cells that can stimulate the productionof antibodies (agglutinins) that combine with theantigen and cause agglutination.
agranulocyte
( ă -gran ′ ū -l ō -s ī t) Nongranular leuko-cyte (monocyte or lymphocyte).
ala;
pl.
alae
( ā ′ l ă , ā ′ l ē ) [L., a wing] Wing-shapedstructure.
aldosterone
(al-dos ′ ter- ō n) Steroid hormone pro-duced by the zona glomerulosa of the adrenal cor-tex that facilitates potassium exchange for sodiumin the distal renal tubule, causing sodium reab-sorption and potassium and hydrogen secretion.
alkaline
(al ′ k ă -l ī n) Solution containing less than10
−7
mol of hydrogen ions per liter; has a pHgreater than 7.0.
alkalosis
(al-k ă -l ō ′ sis) Condition characterized byblood pH of 7.45 or above.
allantois
( ă -lan ′ t ō -is) Tube extending from the em-bryonic hindgut into the umbilical cord; forms theurinary bladder.
allele
( ă -l ē l ′ ) [Gr.,
allelon,
reciprocally] Any oneof a series of two or more different genes that
may occupy the same position or locus on a spe-cific chromosome.
all-or-none principle
When a stimulus is appliedto a cell, an action potential is either produced ornot. In muscle cells, the cell either contracts to themaximum extent possible (for a given condition)or does not contract.
alternative pathway
Part of the nonspecific immunesystem for activation of complement.
alveolar duct
(al-v ē ′ ō -l ă r) Part of the respiratorypassages beyond a respiratory bronchiole; fromit arise alveolar sacs and alveoli.
alveolar gland
Gland in which the secretory unithas a saclike form and an obvious lumen.
alveolar sac
Two or more alveoli that share anopening.
alveolus;
pl.
alveoli
(al-v ē ′ ō -l ŭ s, al-v ē ′ ō -l ī )Cavity. Examples include the sockets into whichteeth fit, the endings of the respiratory system,and the terminal endings of secretory glands.
amino acid
( ă -m ē ′ n ō ) Class of organic acids thatconstitute the building blocks for proteins.
amplitude-modulated signal
(am ′ pli-tood) Sig-nal that varies in magnitude or intensity, such aswith large versus small concentrations of hor-mones.
ampulla
(am-pul ′ l ă , am-pul ′ l ē ) [L., two-handledbottle] Saclike dilatation of a semicircular canal;contains the crista ampullaris. Wide portion ofthe uterine tube between the infundibulum and theisthmus.
amygdala
(a-mig ′ da-la, -l ē ) [L. fr. Gr.,
amygy-dale,
almond] Nucleus in the temporal lobeof the brain, amygdaloid nucleus; also calledamydaloid nuclear complex.
amylase
(am ′ il- ā s) One of a group of starch-splittingenzymes that cleave starch, glycogen, and re-lated polysaccharides.
anabolism
( ă -nab ′ ō -lizm) [Gr.,
anabole,
a raising up]All of the synthesis reactions that occur within thebody; requires energy.
anaerobic respiration
(an- ā r- ō ′ bik) Breakdown ofglucose in the absence of oxygen to produce lacticacid and two ATPs; consists of glycolysis andthe reduction of pyruvic acid to lactic acid.
anal canal
Terminal portion of the digestive tract.
anal triangle
Posterior portion of the perineal regionthrough which the anal canal opens.
analgesic
(an-al-j ē ′ zik) Compound capable of pro-ducing analgesia, without producing anesthesia orloss of consciousness, characterized by reducedresponse to painful stimuli.
anaphase
(an ′ ă -f ā z) Time during cell division whenchromatids divide (or, in the case of first meio-sis, when the chromosome pairs divide).
anastomoses
( ă -nas ′ t ō -m ō ′ sez) Natural communica-tion, direct or indirect, between two blood vesselsor other tubular structures. An opening created bysurgery, trauma, or disease between two or morenormally separate spaces or organs.
anatomical dead air space
Volume of the conduct-ing airways from the external environment downto the terminal bronchioles.
androstenedione
(an-dr ō -st ē n-d ī ′ ō n) Androgenicsteroid of weaker potency than testosterone;secreted by the testis, ovary, and adrenal cortex.
anencephaly
(an ′ en-sef ′ ă -l ē ) [Gr.,
an
+
enkepha-los,
no brain] Defective development of thebrain and absence of the bones of the cranium.Only a rudimentary brainstem and a trace ofbasal ganglia are present.
aneurysm
(an ′ ū -rizm) [Gr.,
eurys,
wide] Dilatedportion of an artery.
angiotensin I
(an-j ē - ō -ten ′ sin) Peptide derived whenrenin acts on angiotensinogen.
angiotensin II
Peptide derived from angiotensinI; stimulates vasoconstriction and aldosteronesecretion; also called active angiotensin.
anion
(an ′ ī -on) Ion carrying a negative charge.
antagonist
(an-tag ′ ŏ -nist) Muscle that works inopposition to another muscle.
anterior chamber
Chamber of the eye between thecornea and the iris.
anterior interventricular sulcus
Groove onthe anterior surface of the heart, markingthe location of the septum between the twoventricles.
anterior pituitary gland
See
adenohypophysis.
antibody
(an ′ t ē -bod- ē ) Protein found in the plasmathat is responsible for humoral immunity; bindsspecifically to antigen.
antibody-mediated immunity
Immunity due to Bcells and the production of antibodies.
anticoagulant
(an ′ t ē -k ō -ag ′ ū -lant) Agent that pre-vents coagulation.
antidiuretic hormone (ADH)
(an ′ t ē -d ī - ū -ret ′ ik)Hormone secreted from the neurohypophysisthat acts on the kidney to reduce the output ofurine; also called vasopressin because it causesvasoconstriction.
antigen
(an ′ ti-jen) [anti(body) + Gr.,
gen,
produc-ing] Substance that induces a state of sensitivityor resistance to infection or toxic substances af-ter a latent period; substance that stimulates thespecific immune system; also called epitope.
antigenic determinant
(an-ti-jen ′ ik) Specific partof an antigen that stimulates an immune systemresponse by binding to receptors on the surface oflymphocytes; also called epitope.
antithrombin
(an-t ē -throm ′ bin) Substance that in-hibits or prevents the effects of thrombin so thatblood does not coagulate.
antrum
(an ′ tr ŭ m) [Gr.,
antron,
a cave] Cavity of anovarian follicle filled with fluid containing estrogen.
anulus fibrosus
(an ′ ū -l ŭ s f ī -br ō ′ sus) [L., fibrousring] Fibrous material forming the outer portionof an intervertebral disk.
anus
( ā ′ n ŭ s) Lower opening of the digestive tractthrough which fecal matter is extruded.
aorta
( ā - ō r ′ t ă ) [Gr.,
aorte
from
aeiro,
to lift up]Large, elastic artery that is the main trunk ofthe systemic arterial system; carries blood fromthe left ventricle of the heart and passes through thethorax and abdomen.
aortic arch
[L., bow] Curve between the ascendingand descending portions of the aorta.
aortic body
One of the smallest bilateral structures,similar to the carotid bodies, attached to a smallbranch of the aorta near its arch; contains chemo-receptors that respond primarily to decreases inblood oxygen; less sensitive to decreases in bloodpH or increases in carbon dioxide.
apex
( ā ′ peks) [L., summit or tip] Extremity of aconical or pyramidal structure. The apex of theheart is the rounded tip directed anteriorly andslightly inferiorly.
Apgar score
Named for U.S. anesthesiologistVirginia Apgar (1909–1974). Evaluation of anewborn infant’s physical status by assigningnumerical values to each of five criteria: ap-pearance (skin color), pulse (heart rate), grimace(response to stimulation), activity (muscle tone),