The outside of the skin, called the epidermis, is a layer of flat, dead cells. These contain keratin to make the skin waterproof and tough. The cells are constantly being worn away. But they are replaced by new cells which move toward the surface and harden. Other cells produce a special pigment called melanin.
Melanin darkens the skin and protects it from strong sunlight.
Under the epidermis is a thicker, more elastic layer called the dermis. Here, sebaceous glands produce an oily substance which helps keep the skin and hair soft and waterproof. Thread-like nerves can sense pain, touch, temperature and pressure. Blood vessels, hair follicles and sweat glands all help control body temperature. Use a reliable mattress or wheelchair cushion.