PHYTO-
PINS-AND-NEEDLES
phyto- A prefix meaning of plant origin.
phytomenadione A form of
vitamin K.
phyto-oestrogens
Oestrogens
that oc-
cur naturally in plants.
pia mater The innermost of the 3 mem-
branes of the
meninges
.
pica A craving to eat non-food substan-
ces such as earth or coal. Pica is common
in early childhood and may occur during
pregnancy. It may also occur in nutri-
tional or iron-deficiency disorders, and
in severe psychiatric disorders.
Pickwickian syndrome An unusual dis-
order characterized by extreme
obesity
,
shallow breathing, and
sleep apnoea
. The
cause is unclear. Symptoms usually im-
prove with weight loss.
PID See
pelvic inflammatory disease.
pigeon toes A minor abnormality in
which the leg or foot is rotated, forcing
the foot and toes to point inwards. The
condition is common in toddlers.
pigmentation Coloration of the skin,
hair, and
iris
of the eyes by
melanin
. The
more melanin present, the darker the
coloration. Blood pigments can also
colour skin (such as in a bruise).
There are many abnormalities of pig-
mentation. Patches of pale skin occur in
psoriasis
,
pityriasis alba
,
pityriasis versi-
color,
and
vitiligo. Albinism
is caused by
generalized melanin deficiency.
Phenyl-
ketonuria
results in a reduced melanin
level, making sufferers pale-skinned and
fair-haired. Areas of dark skin may be
caused by disorders such as
eczema
or
psoriasis, pityriasis versicolor,
chloasma
,
or by some perfumes and cosmetics
containing chemicals that cause
photo-
sensitivity
. Permanent areas of deep
pigmentation, such as freckles and moles
(see
naevus
), are usually due to an
abnormality of
melanocytes
.
Acanthosis
nigricans
is characterized by dark patch-
es of velvet-like, thickened skin. Blood
pigments may lead to abnormal colour-
ing. Excess of the bile pigment bilirubin
in
jaundice
turns the skin yellow, and
haemochromatosis
turns the skin bronze.
piles A common name for
haemorrhoids
.
pill, contraceptive See
oral contracep-
tives.
pilocarpine A drug used to treat
glau-
coma
. It may initially cause blurred vision,
headache, and eye irritation.
pilonidal sinus A pit in the skin, often
containing hairs, in the upper part of
the buttock cleft. The cause is probably
hair fragments growing inwards. Al-
though usually harmless, infection may
occur, causing recurrent, painful ab-
scesses. If a sinus is infected, a wide
area around it is surgically removed.
Recurrence of infection is common, and
plastic surgery is sometimes required.
pimozide An
antipsychotic drug
also
used to treat
Gilles de la Tourette's syn-
drome
. Pimozide may cause sedation, dry
mouth, constipation, and blurred vision.
pimple A small
pustule
or
papule
.
pindolol A
beta-blocker drug
used to
treat
angina pectoris
and
hypertension
.
Possible side effects are typical of other
beta-blocker drugs, except that pindolol
is less likely to cause
bradycardia
.
pineal gland A tiny, cone-shaped struc-
ture deep within the
brain
, whose sole
function appears to be the secretion of
melatonin
in response to changes in light.
PINEAL GLAND
pinguecula A small, noncancerous, yel-
lowish spot on the
conjunctiva
over the
white of the eye. They are common in
elderly people, and may be removed for
cosmetic reasons,
pink-eye See
conjunctivitis.
pinna The fleshy part of the outer ear,
consisting of a flap of cartilage and skin.
It is also called the
auricle
.
pins-and-needles A tingling or prickly
feeling in an area of skin that is usually
449
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