G-10
Glossary
type and are involved in the cellular interactions of fertilization, embry-
onic development, and immunity, and act as an adhesive between cells.
Glycogen
(gli
9
ko-jin) Main carbohydrate stored in animal cells; a poly-
saccharide.
Glycogenesis
(gli
0
ko-jen
9
ĕ-sis) Formation of glycogen from glucose.
Glycogenolysis
(gli
0
ko-jĕ-nol
9
ĭ-sis) Breakdown of glycogen to glucose.
Glycolipid
(gli
0
ko-lip
9
id) A lipid with one or more covalently attached
sugars.
Glycolysis
(gli-kol
9
ĭ-sis) Breakdown of glucose to pyruvic acid—an an-
aerobic process.
Goblet cells
Individual cells (unicellular glands) that produce mucus.
Golgi apparatus
(gol
9
je) Membranous system close to the cell nucleus
that packages protein secretions for export, packages enzymes into lyso-
somes for cellular use, and modifies proteins destined to become part of
cellular membranes.
Gonad
(go
9
nad) Primary reproductive organ; i.e., the testis of the male
or the ovary of the female.
Gonadocorticoids
(gon
0
ah-do-kor
9
tĭ-koidz) Sex hormones, primarily
androgens, secreted by the adrenal cortex.
Gonadotropins
(gon
0
ah-do-trōp
9
inz) Gonad-stimulating hormones
produced by the anterior pituitary.
Graded muscle responses
Variations in the degree of muscle contrac-
tion by changing either the frequency or strength of the stimulus.
Graded potential
A local change in membrane potential that varies di-
rectly with the strength of the stimulus, declines with distance.
Graves’ disease
Disorder resulting from hyperactive thyroid gland.
Gray matter
Gray area of the central nervous system; contains neuronal
cell bodies and their dendrites.
Growth hormone (GH)
Hormone that stimulates growth in general;
produced in the anterior pituitary; also called somatotropin.
Guanine (G)
(gwan
9
ēn) One of two major purines occurring in all
nucleic acids.
Gustation
(gus-ta
9
shun) Taste.
Gyrus
(ji
9
rus) An outward fold of the surface of the cerebral cortex.
Hair follicle
Structure with outer and inner root sheaths extending from
the epidermal surface into the dermis and from which new hair develops.
Hapten
(hap
9
ten) An incomplete antigen; has reactivity but not immu-
nogenicity.
Haversian system
(hah-ver
9
zhen)
See
Osteon.
Heart attack (coronary)
See
Myocardial infarction.
Heart block
Impaired transmission of impulses from atrium to ventricle
resulting in abnormally slow heart rhythms.
Heart murmur
Abnormal heart sound (usually resulting from valve
problems).
Heimlich maneuver
Procedure in which the air in a person’s own lungs
is used to expel an obstructing piece of food.
Helper T cell (T
H
cell)
Type of T lymphocyte that orchestrates cellular
immunity by direct contact with other immune cells and by releasing
chemicals called cytokines; also helps to mediate the humoral response
by interacting with B cells.
Hematocrit
(he-mat
9
o-krit) ±e percentage of total blood volume oc-
cupied by erythrocytes.
Hematoma
(he
0
mah-to
9
mah) Mass of clotted blood that forms at an
injured site.
G protein
Protein that relays signals between extracellular first messen-
gers (hormones or neurotransmitters) and intracellular second messen-
gers (such as cyclic AMP) via an effector enzyme.
Gallbladder
Sac beneath the right lobe of the liver used for bile storage.
Gallstones (biliary calculi)
Crystallized cholesterol that obstructs the
flow of bile from the gallbladder.
Gamete
(gam
9
ēt) Sex or germ cell.
Gametogenesis
(gam
0
eh-to-jen
9
eh-sis) Formation of
gametes
.
Ganglion
(gang
9
gle-on) Collection of nerve cell bodies outside the CNS.
Gap junction
A passageway between two adjacent cells; formed by
transmembrane proteins called connexons.
Gastrin
Hormone secreted in the stomach; regulates gastric juice secre-
tion by stimulating HCl production.
Gastroenteritis
Inflammation of the gastrointestinal tract.
Gastrulation
(gas
0
troo-la
9
shun) Developmental process that produces
the three primary germ layers (ectoderm, mesoderm, and endoderm).
Gene
One of the biological units of heredity located in chromatin; trans-
mits hereditary information.
Genetic code
Refers to the rules by which the base sequence of a DNA
gene is translated into protein structures (amino acid sequences).
Genitalia
(jen
0
ĭ-ta
9
le-ă) ±e internal and external reproductive organs.
Genome
±e complete set of chromosomes derived from one parent (the
haploid genome); or the two sets of chromosomes, i.e., one set from the
egg, the other from the sperm (the diploid genome).
Genotype
(jen
9
o-tīp) One’s genetic makeup or genes.
Germ layers
±ree cellular layers (ectoderm, mesoderm, and endoderm)
that represent the initial specialization of cells in the embryonic body and
from which all body tissues arise.
Gestation period
(jes-ta
9
shun) ±e period of pregnancy; about 280 days
for humans.
Gland
Organ specialized to secrete or excrete substances for further use
in the body or for elimination.
Glaucoma
(glaw-ko
9
mah) Condition in which intraocular pressure
increases to levels that cause compression of the retina and optic nerve;
results in blindness unless detected early.
Glial cells
(gle
9
al)
See
Neuroglia.
Glomerular capsule
(glo-mer
9
yoo-ler) Double-walled cup at end of a
renal tubule; encloses a glomerulus. Also called Bowman’s capsule.
Glomerular filtration rate (GFR)
Rate of filtrate formation by the kidneys.
Glomerulus
(glo-mer
9
u-lus) (1) Cluster of capillaries forming part of the
nephron; forms filtrate; (2) odor-specific processing unit in olfactory bulb.
Glottis
(glah
9
tis) Opening between the vocal cords in the larynx.
Glucagon
(gloo
9
kah-gon) Hormone formed by alpha cells of pancreatic
islets; raises the glucose level of blood.
Glucocorticoids
(gloo
0
ko-kor
9
tĭ-koidz) Adrenal cortex hormones that
increase blood glucose levels and aid the body in resisting long-term
stressors.
Gluconeogenesis
(gloo
0
ko-ne
0
o-jen
9
ĕ-sis) Formation of glucose from
noncarbohydrate molecules.
Glucose
(gloo
9
kōs) Principal blood sugar; a hexose.
Glycerol
(glis
9
er-ol) A modified simple sugar (a sugar alcohol); a build-
ing block of fats.
Glycocalyx (cell coat)
(gli
0
ko-kal
9
iks) A layer of externally facing glyco-
proteins on a cell’s plasma membrane; its components determine blood
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