ANHIDROSIS
ANOREXIA NERVOSA
normally give pleasure. Anhedonia is
often a symptom of
depression.
anhidrosis Complete absence of sweat-
ing. (See also
h}spohidrosis.)
animal experim entation The use of
animals in research to provide informa-
tion about animal biology or, by infer-
ence, human physiology or behaviour.
Animal research has contributed to the
development of drugs, such as vaccines,
and surgical techniques, such as trans-
plant surgery.
However,
because of
ethical concerns, alternative practices,
such as cell cultures, are now used
wherever possible.
animals, diseases from See
zoonosis.
anisometropia Unequal focusing power
in the 2 eyes, usually due to a difference
in size and/or shape of the eyes, that
causes visual discomfort. For example,
one eye may be normal and the other
affected by
myopia
(shortsightedness),
hjspermetropia
(longsightedness),
or
astigmatism
(uneven curvature of the
cornea). Glasses or contact lenses cor-
rect the problem in most cases,
ankle join t The hinge joint between the
foot and the leg. The talus (uppermost
bone in the foot) fits between the 2 bony
protuberances formed by the lower ends
of the tibia (the
shinbone) and the
fibula
(the outer
bone of the lower
leg).
Strong liga-
ments
on
either
side of the ankle
joint give it sup-
port.
The
ankle
allows for up-and-
down
movement
of the foot.
An ankle
sprain
is
one of the most
ANKLE JOINT
Fibula
Ankle joint
common injuries. It is usually caused by
twisting the foot over on to its outside
edge, causing overstretching and bruis-
ing of the ligaments. Violent twisting of
the ankle can cause a combined fracture
and dislocation known as
Pott's fracture.
ankylosing spondylitis
An uncommon
inflammatory disease affecting joints
between the vertebrae of the spine and
the sacroiliac joints (joints between the
spine and pelvis).
The cause of ankylosing spondylitis is
usually unknown, but in some cases the
disease may be associated with
colitis
(inflammation of the colon) or
psoriasis
(a skin disease). Ankylosing spondylitis
may run in families; and about 90 per-
cent of people with the condition have
the genetically determined
histocompat-
ibility antigen
(HLA-B27).
Ankylosing spondylitis usually starts
with pain and stiffness in the hips and
lower back, which are worse after rest-
ing and are especially noticeable in the
early morning Other, less common, symp-
toms include chest pain, painful heels
due to additional bone formation, and
redness and pain in the eyes due to
iri-
tis.
In time, inflammation in the spine
can lead to
ankylosis
(permanent stiff-
ness and limited movement) and
kyphosis
(curvature of the spine).
The condition is diagnosed by
X-rays
and
blood tests
. There is no cure but
treatment with exercises, physiotherapy,
and
anti-inflammatory drugs
can reduce
the pain and limitation of movement.
ankylosis
Complete loss of movement
in a joint caused by fusion of the bony
surfaces. Ankylosis may be due to de-
generation as a result of inflammation,
infection, or injury, or be produced sur-
gically by surgery to fuse a diseased
joint to correct deformity or to alleviate
persistent pain (see
arthrodesis
).
anodontia
Failure of some or all of the
teeth to develop. It may be due to
absence of tooth buds at birth or the
result of damage to developing tooth
buds by infection or other widespread
disease. If only a few teeth are missing,
a
bridge
can fill the gap; if all the teeth
are missing, a
denture
is needed.
anomaly
A deviation from what is ac-
cepted as normal, especially a birth
defect such as a limb malformation.
anorexia
The medical term for loss of
appetite (see
appetite
,
loss of
).
anorexia nervosa
An eating disorder
characterized by severe weight loss and
altered self-image that leads sufferers
to believe they are fat when they are,
in fact, dangerously underweight. Anor-
exia nervosa most often affects teenage
girls and young women, but the inci-
dence in young men is rising.
A
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