AIR EMBOLISM
A
humidifier fever (a lung disease causing
coughing and breathing difficulties).
Air conditioning is also thought to be
a factor in some cases of
sick building
syndrome,
which produces headache,
irritability, and loss of energy.
air embolism
The blockage 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 as a result of
injury or following surgery Air embol-
ism can also occur during scuba-diving
or air-travel accidents, in which lung
tissue ruptures, releasing air into the
bloodstream.
air pollution
See
pollution.
air swallowing
See
aerophagy.
air travel
See
aviation medicine; barotrauma.
airway
A
collective
term
for
the
passages
through which air enters and leaves
the lungs (see
respiratory system).
The
airway is made up of the nasal passages,
the oral cavity, the upper part of the
pharynx
(throat), the larynx
(voice-
box),
the
trachea
(windpipe),
the
bronchi
(the
main
air
passages
to
the lungs), and the bronchioles (the
smaller air passages in the lungs that
branch off from the bronchi).
The term airway is also applied to a
tube that is inserted into the mouth of
an unconscious person to prevent the
tongue
from
obstructing
breathing.
Preservation of the airway can also be
achieved by inserting an
endotracheal
tube
into the trachea, either through the
mouth or nose or via an incision in the
neck, as in a
tracheostomy
operation.
(See also
respiratory system.)
airway obstruction
Narrowing or blockage of the respira-
tory 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.
Certain diseases and disorders,
such as
diphtheria
and
lung cancer,
can
cause obstruction. Additionally, spasm
of the muscular walls of the airway, as
occurs in
bronchospasm
(a feature of
asthma
and
bronchitis),
results in
breath-
ing difficulty.
(See also
rescue breathing;
lung
disorders box.)
akathisia
The inability to sit still, which occas-
ionally occurs as a side effect of an
antipsychotic drug
or, less commonly, as a
complication of
Parkinson’s disease.
akinesia
Complete or almost complete loss of
movement. Akinesia may result from
damage to part of the brain due, for ex-
ample, to a
stroke
or
Parkinson’s disease.
albinism
A rare, inherited disorder that is char-
acterized by a lack of the pigment
melanin,
which gives colour to the skin,
hair, and eyes.
Oculocutaneous albinism (the most
common type of albinism) is transmit-
ted as an autosomal recessive trait (see
genetic disorders).
The
genetic defect
results in deficiency of a specific
enzyme
(a protein that acts as a catalyst); this
deficiency interferes with the produc-
tion of melanin in the affected tissues.
In oculocutaneous albinism, the hair,
skin, and eyes are all affected. The skin
cannot tan and ages prematurely. In
addition,
skin cancers
may develop on
areas of skin exposed to the sun. Less
often, only the eyes are affected. Visual
problems affecting people with albin-
ism include
photophobia
(an intolerance
to bright light),
nystagmus
(abnormal
flickering movements),
myopia
(short-
sightedness), and
squint.
Glasses are usually needed from an
early age, and tinted glasses help to
reduce
photophobia.
If the
skin
is
affected, it should be carefully protected
from the sun.
albumin
The most abundant protein in the
blood
plasma. Albumin is made in the liver
from
amino
acids
that
have
been
absorbed from digested protein.
Albumin 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 in the urine. Albumin also reg-
ulates the movement of water between
tissues and the bloodstream by
osmosis
(the movement of water to an area with
a higher concentration of salts or pro-
teins). (See also
albuminuria.)
Appearance of albinism
Albinism is characterized by the lack of melanin
pigment in the skin, hair, and eyes.
Albinism in an African boy
The condition occurs only rarely, but it is found in
people of all ethnic groups.
albuminuria
The presence of the protein
albumin
in
the urine; a type of
proteinuria.
Norm-
ally, the glomeruli (the filtering units of
the kidneys) do not allow albumin to
pass into the urine. Albuminuria there-
fore
usually
indicates
that
there
is
damage to the kidneys’ filtering mech-
anisms. Such damage may be due to a
kidney
disorder,
such
as
glomerulo-
nephritis
or
nephrotic syndrome,
or it may
be a sign that the kidneys have been
affected by
hypertension.
In
diabetes mel-
litus,
the
presence
of
even
small
amounts of albumin in the urine (a
condition known as microalbuminuria)
is an early indicator of kidney damage.
Albuminuria can be detected by a sim-
ple urine test.
alcohol
A colourless liquid produced from the
fermentation of carbohydrates by yeast.
Also known as ethanol or ethyl alcohol,
alcohol is the active constituent of alco-
holic drinks such as beer, wine, and
spirits. In medicine, alcohol is used as
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