Bma Illustrated Medical Dictionary

normally give pleasure. Anhedonia is

often a symptom of depression.

anhidrosisComplete absence of sweat-

ing. (See also hypohidrosis.)

animal experimentationThe 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

developmentof 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 fromSee zoonosis.

anisometropiaUnequal 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),

hypermetropia (longsightedness), or

astigmatism(uneven curvature of the

cornea). Glasses or contact lenses cor-

rect the problem in most cases.

ankle jointThe 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 sprainis

one of the most

common injuries. Itis 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 spondylitisAn 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 drugscan reduce

the pain and limitation of movement.

ankylosisComplete 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).

anodontiaFailure 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 bridgecan fill the gap; if all the teeth

are missing, a dentureis needed.

anomalyA deviation from what is ac-

cepted as normal, especially a birth

defect such as a limb malformation.

anorexiaThe medical term for loss of

appetite (see appetite,loss of).

anorexia nervosaAn 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.

ANHIDROSIS ANOREXIA NERVOSA

A

Calcaneous

ANKLE JOINT

Fibula

Talus

Ankle joint

Tibia