The skin

The skin is the largest organ of the body. It acts as a barrier to protect the body from injury, control body temperature and prevent loss of body fluids. The two main layers of the skin are the epidermis and dermis.

Epidermis

The epidermis is the top, outer layer of the skin. It contains three main types of cells:

Squamous cells – These flat cells are packed tightly together to make up the top layer of skin. They form the thickest layer of the epidermis.

Basal cells – These block-like cells make up the lower layer of the epidermis. The body makes new basal cells all the time. As they age, they move up into the epidermis and flatten out to form squamous cells. The basal cells sit on a very thin layer of tissue (the basement membrane) that separates the epidermis from the rest of the body.

Melanocytes – These cells sit between the basal cells and produce a dark pigment called melanin that gives skin its colour. When skin is exposed to ultraviolet (UV) radiation, melanocytes make melanin to try to protect the skin from getting burnt. Melanocytes are also found in non-cancerous spots on the skin called moles or naevi.

Dermis

This layer of the skin sits below the epidermis. The dermis is made up of fibrous tissue and contains the roots of hairs (follicles), sweat glands, blood vessels, lymph vessels and nerves. All of these are held in place by collagen and elastin, the proteins that give skin its strength and elasticity.

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