SKIN ALLERGY
SKIN GRAFT
SKIN
Venule
Hair shaft
Dermis
Subcutaneous
fat
Nerve ending
Arrector pili
muscle
Blood vessel
Sweat
Sweat duct
Epidermis
pore
Scaly upper layer
Sebaceous
gland
Hair follicle
Hair bulb
Nerve
Sweat gland
S
sweat glands, sebaceous glands,
blood
and lymph vessels, and sensory receptors
for pressure, temperature, and pain.
skin allergy Irritation of the skin follow-
ing contact with a specific substance that
provokes an inappropriate or exagger-
ated reaction from the
immune system.
There are 2 main types of allergic skin
reaction. In contact allergic
dermatitis,
red, itchy patches develop a few hours
to
2
days after contact with the allergen.
In contact
urticaria
, red, raised areas
appear a few minutes after skin contact.
In some cases,
skin tests
are needed, to
identify the allergen, for contact with it to
be minimized. (See also atopic
eczema.)
skin biopsy Removal of a portion of skin
for laboratory analysis in order to diag-
nose a skin disorder.
skin cancer A malignant tumour in the
skin. Basal cell carcinoma, squamous cell
carcinoma,
and
malignant melanoma
are
common forms related to long-term
exposure to sunlight.
Bowen's disease,
a
rare disorder that can become cancer-
ous, may also be related to sun exposure.
Less common types include
Paget's dis-
ease of the nipple
and
mycosis fungoides
.
Kaposi's sarcoma
is a type usually found
in people with
AIDS
. Most skin cancers
can be cured if treated early.
skin, disorders of the
The skin is vul-
nerable to various disorders, including
birthmarks
and other
naevi
; infections
that may be viral (such as
cold sores
and
warts
), bacterial (for example,
cellulitis)
,
or fungal (such as
tinea
, which causes
athlete's foot
);
rashes
due to vitamin
deficiency or the side effects of drugs;
and tumours, both noncancerous and
cancerous.
Acne
is common in adoles-
cents and is partly related to the action
of
androgen hormones
. Inflammation of
the skin occurs in
dermatitis
,
eczema
,
and
skin allergy
. The skin is also vulner-
able to injuries such as
burns
, cuts, and
bites (see
bites, animal
;
insect bites
).
skin flap A surgical technique in which
a section of
skin
and underlying tissue,
sometimes including muscle, is moved
to cover an area from which skin and tis-
sue have been lost or damaged by injury,
disease, or surgery. Unlike a
skin graft
, a
skin flap retains its blood supply, either
by remaining attached to the donor site
or through reattachment to blood vessels
at the recipient site by
microsurgery
, so
skin flaps adhere well even where there
is extensive loss of deep tissue.
skin graft A technique used to repair
areas of lost or damaged
skin
that are
too large to heal naturally, that are slow
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