HIP, CLICKING
HISTAMINE
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, clicking
A 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
developmenalhip displasia).
hip,
congenital dislocation of
See
developmental hip dysplasia
.
hip
dysplasia,
developmental
See
developmental hip dysplasia.
hippocampus
A structure in the
limbic
system
of the brain. The hippocampus,
consisting of a band of
grey matter
, is
involved with some learning processes
and long-term memory storage.
Hippocratic oath
A 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 replacement
A surgical procedure
to replace all or part of a diseased
hip
joint with an artificial substitute. The
HIP REPLACEM ENT
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 disease
A
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 examination
can show
the narrowed segment of the intestine.
A
biopsy
may be taken. Treatment of
Hirschsprung's disease involves remov-
ing the narrowed segment and rejoining
the normal intestine to the anus.
hirsutism
Excessive 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 as polycystic
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
.)
histamine
A 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 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.
H
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