These are the functions of the skin:

- To act as a barrier, protecting the body from injury

- To keep necessary fluids and proteins in the body

- To protect the body from the harmful effects of ultraviolet rays

- To help control the body's temperature

The skin is divided into two main layers. The outer layer is known as the epidermis, and the inner layer is the dermis.

The epidermis contains three types of cells: on the surface are the flat cells known as squamous cells; below these are round cells called basal cells; between the basal cells are melanocytes.

The dermis contains nerve endings, blood vessels, oils, and sweat glands. It is held together by a protein called collagen.


Melanocytes are cells that produce a pigment called melanin. Melanin gives our skin its natural color. It also protects the skin from the harmful effects of the sun.

When our skin is exposed to sunlight, melanocytes increase the quantity of melanin so as as to absorb potentially harmful ultraviolet rays. This makes the skin take on a tanned hue and is a sign that the skin is trying to protect itself.

People with naturally dark skin have the same number of melanocytes as fair-skinned people, though the former produce more melanin. This means they have more protection against UV rays.

Moles (sometimes called nevi) are a group or set of melanocytes. Most people with pale skin have 10–50 moles on their skin, and sometimes more.


Melanoma is a cancer that usually starts on the skin, either as a mole or on normal-looking skin. About half of all melanomas start skin that has a normal appearance.

More and more people are developing melanoma, and this disease is usually more common among women than men. It is a common type of cancer in people between who are between 15 and 34, although like most types of cancer it is more common in older people.

Dark-skinned people are less likely to develop melanoma than people with fair skin because their skin has more natural protection.

In women, the common place for melanoma to appear is on the legs. In men, melanoma most often occurs on the chest and back.


Melanoma develops from melanocytes that start to grow and divide more rapidly than normal. The disease also tends to spread into the nearby skin layers. When these cells grow out of control, they normally take on the appearance of a dark spot or mole on the skin.

It is important to diagnose and treat melanoma as early as possible. If not eliminated, the melanoma cells may grow down into the deeper layers of the skin containing small blood vessels and lymph vessels. If this happens, the melanoma may travel to other parts of the body.