Fibrin (Ff-brin) An insoluble protein that is essential to blood clot-
ting; formed from fibrinogen by the action of thrombin.
Fibrinogen (fT-BRIN-o-jen) A clotting factor in blood plasma that by
the action of thrombin is converted to fibrin.
-sis) Dissolution of a blood clot by the action
of a proteolytic enzyme, such as plasmin (fibrinolysin), that dis-
solves fibrin threads and inactivates fibrinogen and other blood-
Fibroblast (FT-bro-blast) A large, flat cell that secretes most of the
extracellular matrix material of areolar and dense connective
Fibrous joint (FT-brus) A joint that allows little or no movement, such
as a suture or a syndesmosis.
Fibrous tunic (TOO-nik) The superficial coat of the eyeball, made up
of the posterior sclera and the anterior cornea.
Fight-or-flight response The effects produced upon stimulation of
the sympathetic division of the autonomic nervous system.
Filtration (fil-TRA-shun) The flow of a liquid through a filter (or mem-
brane that acts like a filter) due to a hydrostatic pressure; occurs
in capillaries due to blood pressure.
Filtration membrane Site of blood filtration in nephrons of the
kidneys, consisting of the endothelium and basement membrane
of the glomerulus and the epithelium of the visceral layer of the
glomerular (Bowman's) capsule.
Fissure (FISH-ur) A groove, fold, or slit that may be normal or abnor-
Fixed macrophage (MAK-ro-faj) Stationary phagocytic cell found in
the liver, lungs, brain, spleen, lymph nodes, subcutaneous tissue,
and red bone marrow. Also called a histiocyte (HIS-te-o-sTt).
Flaccid (FLAS-sid) Relaxed, flabby, or soft; lacking muscle tone.
Flagellum (fla-JEL-um) A hairlike, motile process on the extremity of a
bacterium, protozoan, or sperm cell.
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Flatus (FLA-tus) Gas in the stomach or intestines, commonly used to
denote expulsion of gas through the anus.
Flexion (FLEK-shun) Movement in which there is a decrease in the
angle between two bones.
Flexor reflex A protective reflex in which flexor muscles are stimu-
lated while extensor muscles are inhibited.
Follicle (FOL-i-kul) A small secretory sac or cavity; the group of cells
that contains a developing oocyte in the ovaries.
Follicle-stimulating hormone (FSH) Hormone secreted by the ante-
rior pituitary that initiates development of ova and stimulates
the ovaries to secrete estrogens in females, and initiates sperm
production in males.
Fontanel (fon'-ta-NEL) A space filled with mesenchyme where bone
formation is not yet complete, especially between the cranial
bones of an infant's skull.
Foot The terminal part of the lower limb, from the ankle to the toes.
Foramen (fo-RA-men) A passage or opening; a communication
between two cavities of an organ, or a hole in a bone for passage
of vessels or nerves.
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Foramen ovale (fo-RA-men o-VAL-e) An opening in the fetal heart in
the septum between the right and left atria. A hole in the greater
wing of the sphenoid bone that transmits the mandibular branch
of the trigeminal (V) nerve.
Forearm (FOR-arm) The part of the upper limb between the elbow
and the wrist.
Fossa (FOS-a) A furrow or shallow depression.
Fourth ventricle (VEN-tri-kul) A cavity filled with cerebrospinal fluid
within the brain lying between the cerebellum and the medulla
oblongata and pons.
Fracture (FRAK-choor) Any break in a bone.
Frenulum (FREN-u-lum) A small fold of mucous membrane that con-
nects two parts and limits movement.
Frontal plane A plane at a right angle to a midsagittal plane that
divides the body or organs into anterior and posterior portions.
Also called a coronal plane (ko-RO-nal).
Functional residual capacity (re-ZID-u-al) The sum of residual volume
plus expiratory reserve volume; about 2400 mL in males and
1800 mL in females.
Fundus (FUN-dus) The part of a hollow organ farthest from the opening.
Fungiform papilla (FUN-ji-form pa-PIL-a) A mushroomlike elevation
on the upper surface of the tongue appearing as a red dot; most
contain taste buds.
Gallbladder A small pouch, located inferior to the liver, that stores
bile and empties by means of the cystic duct.
Gallstone A solid mass, usually containing cholesterol, in the gallbladder
or a bile-containing duct; formed anywhere between bile canaliculi
in the liver and the hepatopancreatic ampulla (ampulla of Vater),
where bile enters the duodenum. Also called a biliary calculus.
Gamete (GAM-et) A male or female reproductive cell; a sperm cell or
Ganglion (GANG-gle-on) Usually, a group of neuronal cell bodies
lying outside the central nervous system (CNS).
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Gastric glands (GAS-trik) Glands in the mucosa of the stomach com-
posed of cells that empty their secretions into narrow channels
called gastric pits. Types of cells are chief cells (secrete pepsino-
gen), parietal cells (secrete hydrochloric acid and intrinsic factor),
surface mucous and mucous neck cells (secrete mucus), and G
cells (secrete gastrin).
Gastroenterology (gas'-tro-en'-ter-OL-o-je) The medical specialty that
deals with the structure, function, diagnosis, and treatment of
diseases of the stomach and intestines.
Gastrointestinal (gas-tro-in-TES-ti-nal) (GI) tract A continuous tube
extending from the mouth to the anus. Also called the alimentary
Gastrulation (gas'-troo-LA-shun) The migration of groups of cells
from the epiblast that transform a bilaminar embryonic disc into
a tri laminar embryonic disc that consists of the three primary
germ layers; transformation of the blastula into the gastrula.
Gene (JEN) Biological unit of heredity; a segment of DNA located in a
definite position on a particular chromosome; a sequence of DNA
that codes for a particular mRNA, rRNA, or tRNA.