Glossary 587levels of nitrogenous waste products are elevated; caused
by renal insufficiency or failure (Chapter 18).
Ureter(YOOR-uh-ter) The tubular organ that carries
urine from the renal pelvis (kidney) to the urinary blad-
der (Chapter 18).
Urethra(yoo-REE-thrah) The tubular organ that carries
urine from the urinary bladder to the exterior of the body
(Chapter 18).
Urinary bladder(YOOR-i-NAR-ee BLA-der) The organ
that stores urine temporarily and contracts to eliminate
urine by way of the urethra (Chapter 18).
Urinary system(YOOR-i-NAR-ee SIS-tem) The organ
system that produces and eliminates urine; consists of the
kidneys, ureters, urinary bladder, and urethra (Chap-
ter 18).
Urine(YOOR-in) The fluid formed by the kidneys from
blood plasma (Chapter 18).
Uterus(YOO-ter-us) The organ of the female reproductive
system in which the placenta is formed to nourish a
developing embryo-fetus (Chapter 20).
Utricle(YOO-tri-kuhl) A membranous sac in the vestibule
of the inner ear that contains receptors for static equilib-
rium (Chapter 9).—V—
Vaccine(vak-SEEN) A preparation of a foreign antigen that
is administered by injection or other means in order to
stimulate an antibody response to provide immunity to a
particular pathogen (Chapter 14).
Vagina(vuh-JIGH-nah) The muscular tube that extends
from the cervix of the uterus to the vaginal orifice; serves
as the birth canal (Chapter 20).
Vagus nerves(VAY-gus) Cranial nerve pair X; sensory for
cardiovascular and respiratory reflexes; motor to larynx,
bronchioles, stomach, and intestines (Chapter 8).
Valence(VAY-lens) The combining power of an atom when
compared to a hydrogen atom; expressed as a positive or
negative number (Chapter 2).
Valve(VALVE) A structure in a cavity or tube that closes
upon, and thus prevents, backflow of the fluid therein
(from the Latin “a leaf of a double door”) (Chapter 12).
Varicose vein(VAR-i-kohs VAYN) An enlarged, abnor-
mally dilated vein; most often occurs in the legs (Chap-
ter 13).
Vasectomy (va-SEK-tuh-me) A surgical procedure to
remove or sever the ductus deferens; usually done as a
method of contraception in men (Chapter 20).
Vasoconstriction(VAY-zoh-kon-STRIK-shun) A decrease
in the diameter of a blood vessel caused by contraction
of the smooth muscle in the wall of the vessel (Chap-
ter 5).
Vasodilation(VAY-zoh-dye-LAY-shun) An increase in the
diameter of a blood vessel caused by relaxation of the
smooth muscle in the wall of the vessel (Chapter 5).Vasomotor center(VAY-zoh-MOH-ter) The part of the
medulla that regulates the diameter of arteries and veins;
contributes to normal blood pressure (Chapter 8).
Vasopressin(VAY-zoh-PRESS-in) Antidiuretic hormone
(Chapter 8).
Vector(VEK-ter) An arthropod that transmits pathogens
from host to host, usually when it bites to obtain blood
(Chapter 22).
Vein(VAYN) A blood vessel that takes blood from capillar-
ies back to the heart (Chapter 13).
Venous return (VEE-nus ree-TURN) The amount of
blood returned by the veins to the heart; is directly
related to cardiac output, which depends on adequate
venous return (Chapter 12).
Ventilation(VEN-ti-LAY-shun) The movement of air into
and out of the lungs (Chapter 15).
Ventral (VEN-truhl) Toward the front (Syn.—anterior)
(Chapter 1).
Ventral cavity(VEN-truhl KAV-i-tee) Cavity that consists
of the thoracic, abdominal, and pelvic cavities (Chap-
ter 1).
Ventral root(VEN-truhl ROOT) The motor root of a
spinal nerve (Chapter 8).
Ventricle(VEN-tri-kul) 1. A cavity, such as the four ventri-
cles of the brain that contain cerebrospinal fluid. 2. One
of the two lower chambers of the heart that pump blood
to the body or to the lungs (Chapter 8).
Venule(VEN-yool) A small vein (Chapter 13).
Vertebra(VER-te-brah) One of the bones of the spine or
backbone (Chapter 6).
Vertebral canal(VER-te-brahl ka-NAL) The spinal cavity
that contains and protects the spinal cord (Chapter 6).
Vertebral column(VER-te-brahl KAH-luhm) The spine
or backbone (Chapter 6).
Vestibule(VES-ti-byool) 1. The bony chamber of the inner
ear that contains the utricle and saccule (Chapter 9).- The female external genital area between the labia
minor that contains the openings of the urethra, vagina,
and Bartholin’s glands (Chapter 20).
Vestigial organ(ves-TIJ-ee-uhl) An organ that is reduced
in size and function when compared with that of evolu-
tionary ancestors; includes the appendix, ear muscles that
move the auricle, and wisdom teeth (Chapter 16).
Villi(VILL-eye) 1. Folds of the mucosa of the small intes-
tine that increase the surface area for absorption; each vil-
lus contains a capillary network and a lacteal (Chapter
16). 2. Projections of the chorion, an embryonic mem-
brane that forms the fetal portion of the placenta
(Chapter 21).
Virulence(VIR-yoo-lents) The ability of a microorganism
to cause disease; the degree of pathogenicity (Chap-
ter 22).
Virus(VIGH-rus) The simplest type of microorganism,
consisting of either DNA or RNA within a protein shell;
all are obligate intracellular parasites (Chapter 14).
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