Skin, is the body’s largest organ. It’s main job is
to protect your body against the stresses of the environment and
to control the body’s temperature. Skin is in fact the only
organ that comes into direct contact with the outside world.
The skin is made up of 3 main layers. Epidermis, dermis and subcutaneous
Consists of 3 parts. Stratum corneum (horny layer), Keratinocytes
and the basal layer.
Stratum corneum (horny layer)
Is the uppermost layer of skin and prevents the entry of most foreign
substances from entering the body. This also protects the loss of
fluid from the body. The outer layer is constantly being shed.
Keratinocytes (squamous cells)
Contains keratinocytes, (living cells). These are fed to the horny
layer when they are mature. These contain the protein keratin, which
is a substance that adds strength to the outermost layer of the
skin. (this is where a form of skin cancer begins - squamous cell
The deepest layer of the epidermis, is in direct contact with the
dermis and contains basal cells. Basal cells continually divide
forming new keratinocytes which are then fed towards the outer layers.
(basal cell carcinoma, another form of skin cancer begins here)
The basal layer also contains another type of cell called ‘melanocytes’.
These cells produce melanin, which is a pigment that is the source
of tanning. People of all races contain approximately the same number
of melanocytes, however, people of different races will produce
different levels of melanin.
The most dangerous form of skin cancer – melanona –
The dermis contains hair follicles, sweat glands and nerve endings
that allow you to sense the world. Pain and touch receptors act
as a warning that something may be damaging your skin. The dermis
is held together by the proteins collagen and elastin. Collagen
accounts for upto 75% of the weight of the dermis and is responsible
for the elasticity of the skin. The dermis also helps to control
the body’s temperature.
This is the deepest layer of the skin. The subcutis contains a network
of collagen and fat cells that act as a ‘shock absorber’
to help protect the body from injury. They also help to conserve
the body’s heat. Blood vessels branch infinitely from the
subcutis into the dermis, unlike the epidermis which has no direct
Skin types – for exposure to ultraviolet light
(developed by Dr. Thomas Fitzpatrick – Harvard Medical School)
|Skin type I :
||Never tans, always burns (extremely fair skin,
blond hair, blue/green eyes)
|Skin type II :
|| Occasionally tans, usually burns (fair skin, sandy to brown
hair, green/brown eyes)
|Skin type III :
||Often tans, sometimes burns (medium skin, brown hair, brown
|Skin type IV :
||Always tans, never burns (olive skin, brown/black hair, dark
|Skin type V :
|| Never burns, (dark brown skin, black hair, black eyes)
|Skin type VI :
||Never burns, (black skin, black hair, black eyes)