Medical Dictionary Definitions A-Z List
Medical Dictionary Definitions A - Z - «A»:
Acoustic nerve: A cranial nerve concerned with hearing, balance and head position. The acoustic nerve is the 8th cranial nerve. It branches into two parts -- a cochlear part integral to hearing and a vestibular part which mediates the sense of balance and head position. Also called the vestibulococh...
Acoustic neurinoma: A benign tumor that may develop on the hearing and balance nerves near the inner ear. The tumor results from an overproduction of Schwann cells -- small sheet-like cells that normally wrap around nerve fibers like onion skin and help support the nerves. When growth is abnormally ...
Acoustic neurofibromatosis: See: Neurofibromatosis type 2....
Acoustic neuroma: A benign tumor that may develop on the hearing and balance nerves near the inner ear. The tumor results from an overproduction of Schwann cells -- small sheet-like cells that normally wrap around nerve fibers like onion skin and help support the nerves. When growth is abnormally ex...
ACP (American College of Physicians)
ACP (American College of Physicians): See: American College of Physicians....
Acquired: Anything that is not present at birth
but develops some time later. In medicine, the word "acquired"
implies "new" or "added." An acquired condition is "new" in the sense
that it is not genetic (inherited) and "added" in the sense that
was not present at birth.
For example, AIDS (the a...
Acquired deafness: The loss of hearing that occurs or develops some time during a person's life but was not present at birth.
Acquired deafness contrasts to congenital deafness which is present at birth.
The distinction between acquired and congenital deafness specifies only the time that the deafn...
Acquired epileptiform aphasia
Acquired epileptiform aphasia: See Landau-Kleffner syndrome....
Acquired immunity: Immunity acquired by infection or vaccination (active immunity) or by the transfer of antibody or lymphocytes from an immune donor (passive immunity). Acquired immunity is in contrast to innate immunity (natural immunity)....
Acquired immunodeficiency syndrome
Acquired immunodeficiency syndrome: AIDS. AIDS is a disease due to infection with the human immunodeficiency virus (HIV).
Also referred to as acquired immunodeficiency disease....
Acquired mutation: A mutation (a genetic change) acquired by a somatic cell after conception. Acquired mutations occur in somatic cells, not germ cells, and so cannot be transmitted to the children. However, acquired mutations are transmitted to all cells descended from the mutant cell, giving rise...
Acral-lentiginous melanoma: See: Melanoma, acral-lentiginous....
Acrocentric chromosome: A chromosome (one
of the microscopically visible carriers of the genetic material DNA)
with its centromere (the "waist" of the chromosome) located quite
near one end of the chromosome. The "acro-" in acrocentric comes from
the Greek "akron" meaning "the end." Humans have...
inherited disorder causing abnormalities of the skull and
face and the hands and feet.
In acrocephalosyndactyly there is closure too-early of
some of the sutures of the skull (craniosynostosis). This
results in an abnormally shaped head, which is unusually
tall and ...
Acrochordon: A small tag of skin that may have a stalk (a peduncle). An acrochordon may appear on skin anywhere although the favorite locales are the eyelids, neck, armpits (axillae), upper chest, and groin.
Invariably benign, this tiny tumor of the skin usually causes no symptoms unless repeated...