Human skin. Coloured scanning electron micrograph (SEM) of the surface of healthy human skin. The scaly appearance is due to 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. Its structure varies according to location; a distinction is made between the thick skin that covers the hands and feet, and thin skin that covers most of the remaining body surface. The ability of skin to differentiate gives rise to hair, nails, sebaceous glands and sweat glands. Magnification: unknown.