PSEUDOMONAS
PSYCHIATRY
scrotum resembling labia. (See also
hermaphroditism, sex determination.)
pseudomonas Species of rod-like
bac-
teria
that live in soil and decomposing
matter,
pseudomona aeruginosa is
capa-
ble of causing disease in humans and is
present in pus from wounds,
psilocybin An
alkaloid
present in some
mushrooms. It is a
hallucinogenic drug
with properties similar to those of
LSD.
psittacosis A rare illness resembling
influenza
that is caused by the microor-
ganism
chlamydia pstttaci.
The disease
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
anti-
bodies
against
chlamydia pslttaci
in the
blood. Treatment is with
tetracycline
antibiotic drugs. With no treatment,
death may result.
psoas muscle A muscle that bends the
hip upwards towards the chest. There are
2
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
ultraviolet light
to
cause skin darkening or inflammation.
Psoralen drugs may be used in conjunc-
tion with ultraviolet light (a combination
called
PUVA
) to treat
psoriasis
and
viti-
ligo.
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
photosensitivity
.
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.
PSORIASIS
DISCOID PSORIASIS
The exact cause of psoriasis is un-
known. New skin cells are made about
10 times faster than normal. The excess
cells accumulate,
forming thickened
patches covered with dead, flaking skin.
Sometimes, there is also a painful
swelling and stiffness of the joints (see
arthritis
). 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
plaque, psoriasis,
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
pustules
.
In most cases, the condition can be
improved with topical treatments, such
as those containing
corticosteroid drugs
and coal tar. Other treatments include
dithranol ointment,
PUVA
, and drugs
such as
methotrexate.
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
psychoanalytic theory.
)
psychiatry The
branch
of
medicine
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,
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