Transverse plane A plane that divides the body or organs into supe-
rior and inferior portions. Also called a horizontal plane.
Transverse tubules (T tubules) (TOO-bals) Small, cylindrical invaginations
of the sarcolemma of striated muscle fibers (cells) that conduct muscle
action potentials toward the center of the muscle fiber.
Trauma (TRAW-ma) An injury, either a physical wound or psychic disor-
der, caused by an external agent or force, such as a physical blow
or emotional shock; the agent or force that causes the injury.
Tremor (TREM-or) Rhythmic, involuntary, purposeless contraction of
opposing muscle groups.
Tricuspid valve (trT-KUS-p
d) Atrioventricular (AV) valve on the right
side of the heart.
Triglyceride (trf-GLI-cer-Td) A lipid formed from one molecule of glyc-
erol and three molecules of fatty acids that may be either solid
(fats) or liquid (oils) at room temperature; the body's most highly
concentrated source of chemical potential energy. Found mainly
within adipocytes. Also called a neutral fat or a triacylglycerol.
Triiodothyronine (T3) (trl-T-o-do-THT-ro-nen) A hormone produced by
the thyroid gland that regulates metabolism, growth and devel-
opment, and the activity of the nervous system.
Trophoblast (TROF-o-blast) The superficial covering of cells of the
Tropic hormone (TRO-pik) A hormone whose target is another endo-
Trunk The part of the body to which the head and upper and lower
limbs are attached.
Tubal ligation (lT-GA-shun) A sterilization procedure in which the
uterine (fallopian) tubes are tied and cut.
Tubular reabsorption (TOO-byu-lar re-ab-SORP-shun) The movement
of filtrate from renal tubules back into blood in response to the
body's specific needs.
Tubular secretion The movement of substances in blood into renal
tubular fluid in response to the body's specific needs.
Tumor suppressor gene A gene coding for a protein that normally
inhibits cell division; loss or alteration of a tumor suppressor gene
p 5 3
is the most common genetic change in a wide variety
of cancer cells.
Tunica externa (TOO-nik-a eks-TER-na) The superficial coat of an
artery or vein, composed mostly of elastic and collagen fibers.
Also called the adventitia (ad-ven-TISH-a).
Tunica interna (in-TER-na) The deep coat of an artery or vein, consist-
ing of a lining of endothelium, basement membrane, and internal
elastic lamina (in an artery). Also called the tunica intima (IN-ti-
Tunica media (ME-de-a) The intermediate coat of an artery or vein,
composed of smooth muscle and elastic fibers.
Twitch contraction Brief contraction of all muscle fibers (cells) in
a motor unit triggered by a single action potential in its motor
Umbilical cord (um-BIL-i-kal) The long, ropelike structure containing the
umbilical arteries and vein that connect the fetus to the placenta.
um-bil-T-kus) A small scar on the abdomen
that marks the former attachment of the umbilical cord to the
fetus. Also called the navel.
Upper limb The appendage attached at the shoulder girdle, consist-
ing of the arm, forearm, wrist, hand, and digits. Also called upper
Uremia (u-RE-me-a) Accumulation of toxic levels of urea and other
nitrogenous waste products in the blood, usually resulting from
severe kidney malfunction.
Ureter (U-re-ter) One of two tubes that connect the kidney with the
Urethra (u-RE-thra) The duct from the urinary bladder to the exterior
of the body that conveys urine in females and urine and semen in
Urinary bladder (U-ri-ner-e) A hollow, muscular organ situated in
the pelvic cavity posterior to the pubic symphysis; receives urine
via two ureters and stores urine until it is excreted through the
Urine The fluid produced by the kidneys that contains wastes and
excess materials; excreted from the body through the urethra.
Urology (u-ROL-o-je) The specialized branch of medicine that deals
with the structure, function, and diseases of the male and female
urinary systems and the male reproductive system.
Uterine tube (U-ter-in) Duct that transports ova from the ovary to the
uterus. Also called the fallopian tube (fal-LO-pe-an) or oviduct.
Uterus (U-te-rus) The hollow, muscular organ in females that is the
site of menstruation, implantation, development of the fetus, and
labor. Also called the womb.
Utricle (U-tri-kul) The larger of the two divisions of the membranous
labyrinth located inside the vestibule of the inner ear, containing
a receptor organ for static equilibrium.
Uvula (U-vu-la) A soft, fleshy mass, especially the V-shaped pendant
part, descending from the soft palate.
Vagina (va-JTna) A muscular, tubular organ that leads from the uterus
to the vestibule, situated between the urinary bladder and the
rectum of the female.
Vallate papilla (VAL-at pa-PIL-a) One of the circular projections that is
arranged in an inverted V-shaped row at the back of the tongue;
the largest of the elevations on the upper surface of the tongue
that contains taste buds. Also called circumvallate papilla.
Valence (VA-lens) The combining capacity of an atom; the number
of deficit or extra electrons in the outermost electron shell of an
Varicose (VAR-i-kos) Pertaining to an unnatural swelling, as in the
case of a varicose vein.
Vasa recta (VA-sa REK-ta) Extensions of the efferent arteriole of a jux-
tamedullary nephron that run alongside the loop of the nephron
(Henle) in the medullary region of the kidney.
Vasa vasorum (va-SO-rum) Blood vessels that supply nutrients to the
larger arteries and veins.
Vascular (VAS-ku-lar) Pertaining to or containing many blood vessels.