Webster's New World Medical Dictionary

accessory neuropathy
A disease of the acces-
sory nerve, paralysis of which prevents rotation of
the head away from one or both sides and causes
the shoulder to droop. Damage can be confined to
the accessory nerve, or it may also involve the ninth
and tenth cranial nerves, which exit the skull
through the same opening.
accessory placenta
See 
placenta, accessory.
acclimatization to altitude
The process of
adapting to the decrease in oxygen concentration at
a specific altitude. A number of changes must take
place for the body to operate with decreased oxy-
gen. These changes include increasing the depth of
respiration; increasing the pressure in the pul-
monary arteries, forcing blood into portions of the
lung that are normally not used at sea level; manu-
facturing additional oxygen-carrying red blood
cells; and manufacturing extra 2, 4-DPG, a sub-
stance that facilitates the release of oxygen from
hemoglobin to the body tissues. Acclimatization
generally takes 1 to 3 days and occurs after any
significant altitude change above 1,220 meters
(approximately 4,000 feet). Acclimatization is the
body’s natural means of correcting altitude sickness
and the rate of acclimatization depends on the alti-
tude, rate of ascent, and individual susceptibility.
accoucheur
A male obstetrician. An
accoucheuse is a woman obstetrician, or sometimes
a midwife.
ACE
Angiotensin converting enzyme. ACE converts
an angiotensin to its activated form, angiotensin II,
enabling it to function. Angiotensin II constricts
blood vessels and elevates blood pressure.
ACE inhibitor
A drug that inhibits ACE. Using an
ACE inhibitor relaxes the arteries, not only lowering
blood pressure but also improving the pumping effi-
ciency of a failing heart and improving cardiac out-
put in patients with heart failure. ACE inhibitors are
therefore used for blood pressure control and con-
gestive heart failure. ACE inhibitors include
benazepril (brand name: Lotensin), captopril
(brand name: Capoten), lisinopril (brand names:
Zestril, Prinivil), quinapril (brand name: Accupril),
and ramipril (brand name: Altace). Interestingly,
ACE inhibitors were originally developed from the
venom of a Brazilian viper snake.