organelle One of various specialized
structures contained within a body
organic Related to a body
ing organs or an organized structure; or
or to substances
from them. In chemistry, “organic” refers
to certain compounds that contain car-
bon. In medicine, the term indicates the
presence of disease. (See also
organic brain syndrome See
organism A general term for an individ-
ual animal or plant.
organophosphates Highly poisonous
agricultural insecticides that are harm-
ful when absorbed through the skin, by
inhalation, or by swallowing. Among the
many possible symptoms are nausea,
vomiting, abdominal cramps, diarrhoea,
blurred vision, excessive sweating, head-
ache, confusion, and twitching. Severe
poisoning may cause breathing difficulty,
palpitations, seizures, and unconscious-
ness. If left untreated, death may result.
Treatment may include washing out the
) or removing
soiled clothing and washing contami-
nated skin. Injections of
may be needed. With
rapid treatment, people may survive
doses that would otherwise have been
fatal. Long term effects of organophos-
phates in sheep dips are thought to be
responsible for debilitating illness with
neural, muscular, and mental symptoms.
orgasm Intense sensations produced
by a series of muscular contractions at
the peak of sexual excitement. Orgasm
usually lasts for about 3-10 seconds but
can last up to a minute in women.
In men, contractions of the muscles of
the inner pelvis massage seminal fluid
from which it is forcefully propelled via
the urethral orifice (see
Orgasm in women is associated with
irregular contractions of the voluntary
muscles of the walls of the
in some women, of the
by relief of congestion in the pelvic
area. Some women experience multiple
orgasms if stimulation is continued.
Orgasm is followed by a refractory phase
during which there is no physical re-
sponse to further sexual stimulation.
Both men and women may experience
problems with orgasm (see
disorders of; orgasm, lack of).
orgasm, lack of Inability to achieve
orgasm during sexual activity. It may be
due to inhibited sexual desire (see
) or inability to become
aroused or maintain arousal (see
). In men, there may be a
problem achieving orgasm despite nor-
mal arousal (see
ejaculation, disorders of
The problem is common in women; some
may achieve orgasm through
but not during sexual intercourse.
Sometimes it is due to pain during
For both sexes, contributory factors
include problems with technique or in
the relationship, unfamiliarity with sex-
ual responses, psychological problems
(such as anxiety, early sexual trauma, or
inhibitions), and fear of pregnancy.
are sometimes helpful.
orlistat An anti-obesity drug used with a
slimming diet to treat severe obesity.
on the gastrointestinal tract, preventing
the digestion of fats by lipases (pancreat-
Instead of being absorbed,
the fats pass out of the body in faeces.
Side effects are gastrointestinal and
can be minimized by reducing fat in-
take. Flatulence and faecal urgency are
common. Deficiencies of fat-soluble vit-
amins may develop with prolonged use.
ornithosis A disease of birds, caused by
that can cause
orphan drugs Drugs that have been
developed to treat rare conditions but
are not manufactured generally.
used to treat painful muscle spasm due
to soft-tissue injury and
. Side effects include a dry mouth
and blurred vision.
ORT An abbreviation for
ortho- A prefix meaning normal, correct,
or straight, as in
, a branch
of surgery concerned with correcting dis-
orders of the bones and joints.