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Human skin. Coloured scanning electron micrograph (SEM) of the surface of healthy human skin. The scaly appearance is due to the dead outer cells being constantly shed (sloughed off) and replaced. This process is known as desquamation. Skin consists of an outer epidermis supported by an underlying dermis. It accounts for approximately 15% of the body weight of humans. The primary function of skin is to form a barrier between the internal organs and the outside world. It also helps regulate body temperature by releasing sweat and dilating or constricting blood vessels near the surface. Magnification: x570 at 5x7cm size. x1400 at 5x7ins (KEYSTONE/SCIENCE PHOTO LIBRARY/POWER AND SYRED)