OAT CELL CARCINOMA
OCCUPATIONAL DISEASE AND INJURY
oat cell carcinoma A form of
lung can-
cer,
also known as
small cell carcinoma.
obesity A condition in which excess fat
has accumulated in the body. A person
20
per cent above the recommended
weight for his or her height (see
weight)
is obese rather than overweight. About
2
in
5
people in the UK are overweight
and a further
1
in
5
obese.
Obesity is usually caused by consuming
more food than is needed for energy.
Energy requirements are determined by
metabolic rate (see
metabolism)
and level
of physical activity. Family history is
sometimes a factor. Obesity is associated
with some hormonal disorders, but these
are not generally the cause.
Obesity increases the risk of
hyper-
tension, stroke,
and
diabetes mellitus
type
2
.
Coronary artery disease
is more com-
mon, particularly in obese men under
40
. Obesity in men is also associated
with increased risk of cancer of the colon,
rectum, and prostate, and, in women, of
the breast, uterus, and cervix. Extra
weight may aggravate
osteoarthritis
.
The first line of treatment is a slimming
diet (see
weight reduction
) plus regular
exercise. Drugs such as appetite sup-
pressants are rarely used due to their
side effects.
Wiring of the jaws,
stapling
of the stomach, and intestinal bypass
operations are attempted only if obesity
is endangering a person's health.
obsessive-compulsive disorder A psy-
chiatric condition in which a person is
dogged by persistent ideas (obsessions)
that lead to repetitive, ritualized acts
(compulsions). Obsessions are com-
monly based on fears about security or
becoming infected. In obsessional rum-
ination, there is constant brooding over
a word, phrase, or unanswerable prob-
lem. Compulsions may occur frequently
enough to disrupt work and social life.
The disorder is often accompanied by
depression
and
anxiety.
If severe, a per-
son may become housebound.
The disorder usually starts in adoles-
cence. Genetic factors, an obsessive
personality, or a tendency to neurotic
symptoms may contribute. Some types
of brain damage, especially in
enceph-
alitis,
can cause obsessional symptoms.
Many sufferers respond well to
beha-
viour therapy,
which may be combined
with
antidepressant drugs
, but symp-
toms may recur under stress.
obstetrics The branch of medicine con-
cerned with
pregnancy
and
antenatal
care
,
childbirth
, and
postnatal care
. It is
also the study of the structure and func-
tion of the female
reproductive system
.
(See also
gynaecology.)
obstructive airways disease See
pul-
monary disease, chronic obstructive.
occiput The lower back part of the head,
where it merges with the neck.
occlusion Blockage of a passage, canal,
opening, or vessel in the body. This may
be due to disease (for example, a
pul-
monary embolism
) or medically induced.
Occlusion also describes eye-patching
for
amblyopia,
and the relationship
between the upper and lower teeth when
the jaw is shut. (See also
malocclusion.)
occult Hidden or obscure, such as occult
blood in a sample of faeces.
occult blood, faecal The presence in
the faeces of blood that cannot be seen
by the naked eye, but can be detected
by chemical tests. Such tests are widely
used in screening for cancer of the colon
(see
colon, cancer
of). Faecal occult
blood may also be a sign of a gastroin-
testinal disorder such as
oesophagitis
,
gastritis,
or
stomach cancer;
cancer of
the intestine (see
intestine, cancer
of);
rectal cancer (see
rectum, cancer of
);
diverticular disease
;
polyps
in the colon;
ulcerative colitis
; or irritation of the
stomach or intestine by drugs such as
aspirin. (See also
rectal bleeding.)
occupational disease and injury Ill-
nesses, disorders, or injuries that result
from exposure to chemicals or dust, or
are due to physical, psychological, or bio-
logical factors in the workplace.
Pneumoconiosis
is
fibrosis
of the lung
due to inhalation of industrial dusts,
such as coal.
Asbestosis
is associated
O
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