scrotum resembling labia. (See also
hermaphroditism, sex determination.)
pseudomonas Species of rod-like
that live in soil and decomposing
pseudomona aeruginosa is
ble of causing disease in humans and is
present in pus from wounds,
present in some
mushrooms. It is a
with properties similar to those of
psittacosis A rare illness resembling
that is caused by the microor-
is contracted by inhaling dust contain-
ing the droppings of infected birds, such
as pigeons or poultry. Most cases occur
among poultry farmers, pigeon owners,
and people working in pet shops. Com-
mon symptoms are severe headache,
fever, and cough, developing a week or
more after infection. Other symptoms
may include muscle pains, sore throat,
nosebleed, lethargy, depression, and, in
some cases, breathing difficulty.
A diagnosis is made by finding
blood. Treatment is with
antibiotic drugs. With no treatment,
death may result.
psoas muscle A muscle that bends the
hip upwards towards the chest. There are
parts: psoas major and psoas minor.
Psoas major acts to flex the hip and
rotate the thigh inwards. Psoas minor
bends the spine down to the pelvis.
psoralen drugs Drugs containing chem-
icals called psoralens, which occur in
some plants and are present in some
perfumes. When absorbed into the skin,
psoralens react with
cause skin darkening or inflammation.
Psoralen drugs may be used in conjunc-
tion with ultraviolet light (a combination
) to treat
Overexposure to ultraviolet light
during treatment, or to too high a dose
of a psoralen drug, may cause redness
and blistering of the skin. Psoralens in
perfumes may cause
psoriasis A common skin disease char-
acterized by thickened patches of red,
inflamed skin, often covered by silvery
scales. It usually appears between ages
10 and 30, tends to run in families, and
affects men and women equally.
The exact cause of psoriasis is un-
known. New skin cells are made about
10 times faster than normal. The excess
patches covered with dead, flaking skin.
Sometimes, there is also a painful
swelling and stiffness of the joints (see
). Psoriasis tends to recur in
attacks, which may be triggered by fac-
tors such as emotional stress, skin
damage, and physical illness.
There are different forms of the disor-
der. The most common is discoid, or
in which patches
appear on the trunk, limbs, and scalp.
Guttate psoriasis occurs most often in
children, and consists of many small
patches that develop over a wide area
of skin. Pustular psoriasis is character-
ized by small
In most cases, the condition can be
improved with topical treatments, such
as those containing
and coal tar. Other treatments include
, and drugs
Psoriasis is usu-
ally a long-term condition.
psych- A prefix meaning mental pro-
cesses or activities, as in psychology.
psyche A term meaning mind. (See also
concerned with the study, prevention,
and treatment of mental illness and
emotional and behavioural problems.
Psychiatrists usually conduct exami-
nations of physical and mental state,