Webster's New World Medical Dictionary

vitamin P
See 
bioflavinoid.
vitamin therapy
The use of vitamins to prevent
or cure disease, often as a complementary therapy
to accompany medication or other treatments. One
variant on this theme, megavitamin therapy, is still
rather controversial. It is important to consult a
physician before adding vitamin supplements to a
health regimen. See also Appendix C, “Vitamins.”
vitelline duct
See 
yolk stalk.
vitiligo
A condition in which the skin turns white
due to the loss of pigment from the melanocytes,
cells that produce the pigment melanin that gives
the skin color. In vitiligo, the melanocytes are
destroyed, leaving depigmented patches of skin. The
hair that grows in areas affected by vitiligo may also
turn white. The skin is not otherwise damaged.
People with vitiligo must protect their skin from
exposure to the sun. Also known as piebald skin
and acquired leukoderma.
vitreous humor
A clear, jelly-like substance that
fills the middle of the eye.
vocal cord
One of the two small bands of muscle
that form a V-shape within the larynx. When a per-
son breathes, the vocal cords relax, and air moves
through the space between them without making a
sound. When a person talks or sings, the vocal
cords tighten up and move closer together. Air from
the lungs is forced between them, making them
vibrate to produce sound, much like the strings of a
guitar. The tongue, lips, and teeth form that sound
into words. See also 
larynx.
voice box
See 
larynx.
void
To urinate. The term void is also sometimes
used to indicate the elimination of solid waste 
(defecation).
volar
Pertaining to the palm or the sole. For
example, the volar surface of the forearm is the 
portion of the forearm that is on the same side as
the palm of the hand.