AVERSION THERAPY
AZTREONAM
A
aversion therapy
An outdated form of
behaviour therapy
in which unpleasant
stimuli, such as electric shocks, are
administered at the same time as an
unwanted behaviour in an attempt to
alter behavioural patterns.
aviation medicine
The medical spe-
ciality concerned with the physiological
effects of air travel and with the causes
and treatment of medical problems that
may occur during a flight.
avulsed tooth
A tooth that has become
completely dislodged from its socket
following an injury. If the tooth is kept
moist, and treatment is sought immedi-
ately, reimplantation may be possible
(see
reimplantation, dental).
avulsion
The tearing away of a body
structure from its point of attachment.
For example, excessive contraction of a
tendon
may avulse a small piece of
bone at its attachment point. Avulsion
may be due to an injury or be per-
formed as part of a surgical procedure.
axilla
The medical name for the armpit.
axis
The 2nd cervical
vertebra
in the
human
spine.
The axis is attached by a
pivot joint to the
atlas,
the topmost ver-
tebra, which in turn is attached to the
base of the skull. The pivot joint allows
the head to turn to either side.
axon
The thin, elongated part of a
neu-
ron
(nerve cell) that conducts nerve
impulses. Many axons in the body are
covered with a fatty
myelin
sheath.
NERVE CELL
Ayurvedism
See
Indian medicine.
azathioprine
An
immunosuppressant drug
used to treat severe
rheumatoid arthritis
and other
autoimmune disorders.
It is
also used to prevent organ rejection
after
transplant surgery
Increased sus-
ceptibility to infection is a side effect.
azelaic acid
A
topical
drug used to treat
mild to moderate
acne
.
azithromycin
A
macrolide
antibiotic
drug
used to treat infections of the skin,
chest, throat, and ears. Azithromycin is
also used to treat genital infections due
to chlamydia (see
chlamydial infections).
azoospermia
The absence of sperm from
semen, causing
infertility
in males. Azoo-
spermia may be caused by a disorder
present at birth or that develops later in
life or after
vasectomy.
Congenital azoospermia may be due
to a
chromosomal abnormality
such as
Klinefelter's syndrome;
failure of the
testes to descend into the scrotum;
absence of the vasa deferentia (ducts
that carry sperm from the testes to the
seminal vesicles); or
cystic fibrosis
.
In some males, azoospermia may be
the result of hormonal disorders affect-
ing the onset of puberty. Another cause
is blockage of the vasa deferentia,
which may follow a
sexually transmitted
infection
,
tuberculosis
, or surgery on the
groin. Azoospermia can also be the re-
sult of damage to the testes. This can
follow
radiotherapy
, treatment with cer-
tain drugs, and prolonged exposure to
heat, or the effects of occupational
exposure to toxic chemicals.
If the cause is treatable, sperm pro-
duction may restart. However, in some
cases, the testes will have been perma-
nently damaged.
AZT
The abbreviation for azidothymi-
dine, the former name for
zidovudine.
aztreonam
An
antibiotic
used to treat
some types of
meningitis
and infections
by certain types of bacteria, including
PSEUDOMONAS.
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