ANHIDROSIS
A
anhidrosis
Complete absence of sweating. (See also
hypohidrosis.)
animal experimentation
The use of live animals in research and
safety testing to provide information
about animal biology or, by inference,
human physiology or behaviour. Animal
research has contributed to the develop-
ment of surgical techniques, such as
transplant surgery and drugs, such as vac-
cines. Due to ethical concerns, however,
alternative practices, such as cell cul-
tures, are now used whenever possible.
animals, diseases from
See
zoonosis.
anion
An
ion
of negative charge, such as a
chloride ion. (See also
electrolyte.)
anisometropia
Unequal focusing power in the two
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),
hypermet-
ropia
(longsightedness), or
astigmatism
(uneven curvature of the cornea). Glas-
ses
or
contact
lenses
correct
the
problem in most cases.
ankle joint
The hinge joint between the foot and
the leg. The talus (uppermost bone in
the foot) fits between the two bony
protuberances formed by the lower
ends of the tibia (shinbone) and the
fibula (outer bone of the lower leg).
Strong ligaments on either side of the
ankle joint give it support. The ankle
joint allows for up-and-down move-
ment of the foot.
DISORDERS
An ankle
sprain
is one of the most
common injuries. It is usually caused
by twisting of the foot over on to its
outside edge, which causes overstretch-
ing
and bruising
of the ligaments.
Severe sprains can result in tearing of
the ligaments, which may need to be
repaired surgically.
Violent twisting of the ankle can
result in a combined fracture and dis-
location, known as
Pott’s fracture,
in
which the fibula breaks above the ankle
and either the tibia breaks or the lig-
aments tear,
resulting in
dislocation
of the ankle.
ankylosing spondylitis
An uncommon inflammatory disease
affecting joints between the vertebrae of
the spine and the sacroiliac joints (the
joints
between
the
spine
and
the
pelvis).
Ankylosing
spondylitis
may
also affect other large joints, such as
those in the hips.
CAUSES AND INCIDENCE
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
histocompati-
bility antigen
(HLA-B27).
SYMPTOMS
Ankylosing
spondylitis
usually
starts
with pain and stiffness in the hips and
lower back that are worse after resting
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
iritis
(inflammation of the iris). In time,
inflammation in the spine can lead to
ankylosis
(permanent stiffness and limi-
ted movement) and
kyphosis
(curvature
of the spine).
DIAGNOSIS AND TREATMENT
Ankylosing spondylitis can be diagnosed
by
X-rays
and
blood tests.
There is no
cure, but treatment with a programme
of exercise and physiotherapy and
anti-
inflammatory drugs
can reduce the pain
and limitation of movement. In some
cases, DMARDs
(see
disease-modifying
antirheumatic drugs)
are also prescribed.
To
prevent
curvature
of the
spine,
patients are taught breathing exercises
and exercises to improve posture.
ankylosis
Complete loss of movement in a joint
that results from fusion of the bony
surfaces. Ankylosis may be caused by
degeneration as a result of inflamma-
tion, infection, or injury. The condition
can also be produced surgically by an
operation to fuse a diseased joint to cor-
rect deformity or to alleviate persistent
pain (see
arthrodesis).
(See also
anky-
losing spondylitis.)
annular
A term meaning shaped like a ring.
Annular is a description applied to cer-
tain body structures, such as ligaments,
and, in dermatology, to the appearance
of skin rashes, such as ringworm. The
term may also be applied to a cancer
that encircles an organ.
anodontia
Failure of some or all of the teeth to
develop. Anodontia, which can be par-
tial or total, may be due to the absence
of tooth buds at birth, or it may be the
result of damage to developing tooth
buds by infection or other widespread
disease. Both primary and permanent
teeth may be affected. Partial anodontia
is far more common than total.
If only a few teeth are missing, a den-
tal
bridge
(false teeth that are attached
to natural teeth on either side of the
gap) can be fitted. If all the teeth are
missing, a
denture
is required. Recently,
however, dental implants (see
implant,
dental
) have become the treatment of
choice in selected cases (in which the
individual has the correct anatomy and
bone density).
anomaly
A deviation from what is accepted as
normal, especially a birth defect such as
a limb malformation.
Anopheles
A genus of disease-transmitting mosqui-
toes, many species of which are carriers
of
malaria.
(See also
mosquito bites.)
anorexia
The medical term for loss of appetite
(see
appetite, loss of).
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