Bma Illustrated Medical Dictionary

the acetabulum, a cup-like cavity in the
pelvis. Tough ligaments attach the femur
to the pelvis, further stabilizing the
joint and providing it with the necessary
strength to support the weight of the
body and take the strain of leg move-
ments. The structure of the hip allows a
considerable range of leg movement.
hip, clickingA fairly common condition
in adults in which a characteristic click-
ing is heard and felt during certain
movements of the hip joint. Clicking hip
is caused by a tendon slipping over the
bony prominence on the outside of the
femur, and does not indicate disease.
Clicking of the hip that can be heard
during examination of newborn babies
indicates possible dislocation of the hip
(see developmenal hip displasia).
hip, congenital dislocation ofSee
developmental hip dysplasia.
hip dysplasia, developmentalSee
developmental hip dysplasia.
hippocampusA structure in the limbic
systemof the brain. The hippocampus,
consisting of a band of grey matter, is
involved with some learning processes
and long-term memory storage.
Hippocratic oathA set of ethical prin-
ciples derived from the writings of the
Greek physician Hippocrates that is
concerned with a doctor’s duty to work
for the good of the patient.
hip replacementA surgical procedure
to replace all or part of a diseased hip
joint with an artificial substitute. The

HIP REPLACEMENT

replacement is most often carried out in

older people whose joints are stiff and

painful as a result of osteoarthritis. It may

also be needed if rheumatoid arthritis

has spread to the hip joint or if the top

end of the femur is badly fractured (see

femur, fracture of).

Hirschsprung’s diseaseA congenital

disorder in which the rectum, and

sometimes the lower part of the colon,

lack the ganglion cells that control the

intestine’s rhythmic contractions. The

affected area becomes narrowed and

blocks the movement of faecal material.

The disease is rare and tends to run in

families. It occurs about 4 times more

often in boys. Symptoms, which include

constipation and bloating, usually de-

velop in the first few weeks of life, but

may become evident in infancy or early

childhood. The child usually has a poor

appetite and may fail to grow properly.

A barium X-ray examinationcan show

the narrowed segment of the intestine.

A biopsymay be taken. Treatment of

Hirschsprung’s disease involves remov-

ing the narrowed segment and rejoining

the normal intestine to the anus.

hirsutismExcessive hairiness, particular-

ly in women. The additional hair is coarse

and grows in a male pattern on the face,

trunk, and limbs. Hirsutism is a symptom

of certain conditions, such aspolycystic

ovary syndrome (see ovary, polycystic)

and congenital adrenal hyperplasia, in

which the level of male hormones in the

blood is abnormally high. Hirsutism

can also be a result of taking anabolic

steroids (see steroids, anabolic). More

commonly, however, hirsutism is not a

sign of any disorder; it occurs in many

normal women, especially after the

menopause. (See also hypertrichosis.)

histamineA chemical that is present in

cells (mainly mast cells) throughout the

body that is released during an allergic

reaction (see allergy). Histamine acti-

vates 2 main types of receptors, H 1 and

H 2. H 1 activation is responsible for the

swelling and redness that occur in

inflammation. It also narrows the air-

ways in the lungs and causes itching. H 2

activation stimulates acid production

by the stomach. These effects can be

counteracted by antihistamine drugs.

HIP, CLICKING HISTAMINE

H

Pelvis

Head of femur

(thighbone)

removed

Skin

incision

Shaft of

femur

Area of

pelvis

hollowed

out

ARTIFICIAL

HIP JOINT

Pelvic socket

Femoral

component