(a lung disease causing coughing and
breathing difficulty).
air embolismBlockage of a small artery
by an air bubble carried in the blood.
Air embolism is rare. In most cases, it is
caused by air entering the circulation
through a vein, either due to injury or
surgery. Air embolism can also occur
during diving or air travel accidents, in
which lung tissue ruptures, releasing
bubbles into the bloodstream.
air pollutionSee pollution.
air swallowingSee aerophagy.
airwayA collective term for the pas-
sages through which air enters and
leaves the lungs (see respiratory sys-
tem). The term is also applied to a tube
inserted into the mouth of an uncon-
scious person to prevent the tongue
from obstructing breathing.
airway obstructionNarrowing or block-
age of the respiratory passages. The
obstruction may be due to a foreign
body, such as a piece of food, that
becomes lodged in part of the upper
airway and may result in choking. Cer-
tain disorders, such as diphtheriaand
lung cancer, can cause obstruction.
Additionally, spasm of the muscular
walls of the airway, as occurs in bron-
chospasm(a feature of asthma), results
in breathing difficulty.
akathisiaAn inability to sit still, occa-
sionally occurring as a side effect of an
antipsychotic drugor, less commonly, as
a complication of Parkinson’s disease.
akinesiaComplete or almost complete
loss of movement. It may be a result of
damage to part of the brain due, for ex-
ample, to a strokeor Parkinson’s disease.
albinismA rare genetic disordercharac-
terized by a lack of the pigment melanin,
which gives colour to the skin, hair, and
eyes. In oculocutaneous albinism (the
most common type), the hair, skin, and
eyes are all affected. Less often, only
the eyes are affected. In both forms,
skin cannot tan and ages prematurely,
and skin cancersmay develop on areas
exposed to the sun. Visual problems of
people with albinism include photopho-
bia, nystagmus, squint, and myopia.
Glasses are usually needed from an
early age; and tinted glasses help to
reduce photophobia.albuminThe most abundant protein in
the bloodplasma. Albumin is made in
the liver from amino acids. It helps to
retain substances (such as calcium,
some hormones, and certain drugs) in
the circulation by binding to them to
prevent them from being filtered out by
the kidneys and excreted. Albumin also
regulates the movement of water bet-
ween tissues and the bloodstream by
osmosis. (See also albuminuria.)
albuminuriaThe presence of the pro-
tein albuminin the urine; a type of
proteinuria. Normally, the glomeruli (the
filteringunits of the kidneys) do not
allow albumin to pass into the urine.
Albuminuria therefore usually indicates
that there is damage to the kidneys’
filtering mechanisms. Such damage
may be due to a kidney disorder, such
as glomerulonephritisor nephrotic syn-
drome, or may be a sign that the kidneys
have been affected by hypertension.
Albuminuria can be detected by a sim-
ple urine test.
alcoholA colourless liquid produced
from the fermentation of carbohydrates
by yeast. Also known as ethanol, alco-
hol is the active constituent of drinks
such as beer and wine. In medicine, it is
used as an antiseptic and solvent. Meth-
anolis a related, highly toxic substance.
Alcohol is a drug and produces a wide
range of mental and physical effects.
The effect of alcohol on the central
nervous system is as a depressant,
decreasing its activity and thereby
reducing anxiety, tension, and inhibi-
tions. In moderate amounts, alcohol
produces a feeling of relaxation, confi-
dence, and sociability. However, alcohol
slows reactions, and the more that is
drunk, the greater is the impairment of
concentration and judgement. Exces-
sive consumption of alcohol results in
poisoning or acute alcohol intoxication,
with effects ranging from euphoria to
unconsciousness.
Short-term physical effects of alcohol
include peripheral vasodilation(widen-
ing of the small blood vessels), which
causes the face to flush, and increased
flow of gastric juices, which stimulates
the appetite. Alcohol increasessexual
confidence, but high levels can causeAIR EMBOLISM ALCOHOLA