Generator potential The graded depolarization that results in a
change in the resting membrane potential in a receptor (special-
ized neuronal ending); may trigger a nerve action potential (nerve
impulse) if depolarization reaches threshold.
Genetic engineering The manufacture and manipulation of genetic
Genetics The study of genes and heredity.
Genitalia (jen'-i-TA-le-a) Reproductive organs.
Genome (JE-nom) The complete set of genes of an organism.
Genotype (JE-no-tTp) The genetic makeup of an individual; the combi-
nation of alleles present at one or more chromosomal locations,
as distinguished from the appearance, or phenotype, that results
from those alleles.
Geriatrics (jer'-e-AT-riks) The branch of medicine devoted to the
medical problems and care of elderly persons.
Gestation (jes-TA-shun) The period of development from fertilization
to birth.
Gingivae (jin-JI-ve) Gums. They cover the alveolar processes of the
mandible and maxilla and extend slightly into each socket.
Gland Specialized epithelial cell or cells that secrete substances;
may be exocrine or endocrine.
Glans penis (GLANZ PE-nis) The slightly enlarged region at the distal
end of the penis.
Glaucoma (glaw-KO-ma) An eye disorder in which there is increased
intraocular pressure due to an excess of aqueous humor.
Gliding joint A synovial joint having articulating surfaces that are
usually flat, permitting only side-to-side and back-and-forth move-
ments, as between carpal bones, tarsal bones, and the scapula
and clavicle.
Glomerular capsule (glo-MER-u-lar) A double-walled globe at the
proximal end of a nephron that encloses the glomerular capillar-
ies. Also called Bowman's capsule (BO-manz).
Glomerular filtrate (glo-MER-u-lar FIL-trat) The fluid produced when
blood is filtered by the filtration membrane in the glomeruli of the
Glomerular filtration The first step in urine formation in which sub-
stances in blood pass through the filtration membrane and the
filtrate enters the proximal convoluted tubule of a nephron.
Glomerular filtration rate (GFR) The total volume of fluid that enters
all the glomerular (Bowman's) capsules of the kidneys in 1
about 100-125 mL/min.
Glomerulus (glo-MER-u-lus) A rounded mass of nerves or blood
vessels, especially the microscopic tuft of capillaries that is sur-
rounded by the glomerular (Bowman's) capsule of each kidney
P lu r a l
is glomeruli.
Glottis (GLOT-is) The vocal folds (true vocal cords) in the larynx plus
the space between them (rima glottidis).
Glucagon (GLOO-ka-gon) A hormone produced by the alpha cells of
the pancreatic islets (islets of Langerhans) that increases blood
glucose level.
Glucocorticoids (gloo-ko-KOR-ti-koyds) Hormones secreted by the
cortex of the adrenal gland, especially cortisol, that influence
glucose metabolism.
Gluconeogenesis (gloo'-ko-ne-o-JEN-e-sis) The synthesis of glucose
from certain amino acids or lactic acid.
Glucose (GLOO-kos) A six-carbon sugar, C6H12O6, that is a major
energy source for the production of ATP by body cells.
Glucosuria (gloo'-ko-SOO-re-a) The presence of glucose in the urine;
may be temporary or pathological.
Glycogen (GLT-ko-jen) A highly branched polymer of glucose con-
taining thousands of subunits; functions as a compact store of
glucose molecules in liver and muscle fibers (cells).
Glycogenesis (glT'-ko-JEN-e-sis) The chemical reactions by which
many molecules of glucose are used to synthesize glycogen.
Glycogenolysis (glT-ko-je-NOL-i-sis) The breakdown of glycogen into
Glycolysis (glT-KOL-i-sis) Series of chemical reactions in the cytosol of
a cell in which a molecule of glucose is split into two molecules of
pyruvic acid with the net production of two ATPs.
Goblet cell A goblet-shaped unicellular gland that secretes mucus;
present in epithelium of the airways and intestines.
Goiter (GOY-ter) An enlarged thyroid gland.
Golgi complex (GOL-je) An organelle in the cytoplasm of cells consist-
ing of three to twenty flattened sacs (cisternae), stacked on one
another, with expanded areas at their ends; functions in process-
ing, sorting, packaging, and delivering proteins and lipids to the
plasma membrane, lysosomes, and secretory vesicles.
Gomphosis (gom-FO-sis) A fibrous joint in which a cone-shaped peg
fits into a socket.
Gonad (GO-nad) A gland that produces gametes and hormones; the
ovary in the female and the testis in the male.
Gonadotropic hormone Anterior pituitary hormone that affects the
Gray matter Area in the central nervous system and ganglia contain-
ing neuronal cell bodies, dendrites, unmyelinated axons, axon
terminals, and neuroglia; Nissl bodies impart a gray color and
there is little or no myelin in gray matter.
Greater omentum (o-MEN-tum) A large fold in the serosa of the
stomach that hangs down like an apron anterior to the
Greater vestibular glands (ves-TIB-u-lar) A pair of glands on either
side of the vaginal orifice that open by a duct into the space
between the hymen and the labia minora. Also called Bartholin's
glands (BAR-to-linz).
Groin (GROYN) The depression between the thigh and the trunk; the
inguinal region.
Gross anatomy The branch of anatomy that deals with structures
that can be studied without using a microscope. Also called mac-
roscopic anatomy.
Growth An increase in size due to an increase in (1) the number of
cells, (2) the size of existing cells as internal components increase
in size, or (3) the size of intercellular substances.
Gustatory (GUS-ta-to'-re) Pertaining to taste.
Gynecology (gT'-ne-KOL-o-je) The branch of medicine dealing with
the study and treatment of disorders of the female reproductive
530 Glossary
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