With up to two square meters of area and a weight of up to 12 kilograms, the skin is the largest human organ and accomplishes a wide variety of tasks. With the help of about 1.5 million tiny nerve endings in the skin, it is possible to perceive vibrations and pain, to feel, and to sense pressure and temperature stimuli. As an “absorption organ” the skin can absorb substances from the environment into the body – for example, when applying care products. With the acid mantle, the skin prevents germs from penetrating the body. By excreting sweat, it protects us from overheating. And of course the skin is a highly specialized protective barrier against moisture loss, cold, ultraviolet light, mechanical irritations, and pathogens.
The epidermis is the outermost layer of the skin which in turn consists of several cell layers. In the lowermost layer new skin cells (keratinocytes) are generated which thereafter move to skin´s surface. Within two weeks only, they move to the top of the skin, die, harden, and build a layered scaffold of cornified cells which stabilizes water-impermeable lipid membranes. At the top of the skin single corneocytes scale off. In this way the skin completely renews itself approximately once every four weeks. Also situated in the lower region of the epidermis are the pigment cells (melanocytes) which generate the pigment melanin and ensure that on exposure to UV- radiation the skin develops a protective tan.
The dermis is markedly thicker than the epidermis and consists of two layers: the relatively thin papillary and the thicker reticular layer. The surface of the papillary layer with its many bumps (papillae) interlocks with the epidermis and serves as its basement. Every papilla is supplied by a tiny capillary vessel. Also situated within the papillary layer are defensive cells, lymphatic vessels and endings of nerve fibres able to perceive vibrations and sensations of touch. Both dermal layers contain a network of collagen and elastic strands synthesized by fibroblasts which make the skin more elastic. This network is continued into the reticular layer.
The Subcutis is situated below the dermis and consists of connective and fatty tissue. It not only serves as a fat storage, but also as padding, shock absorber and insulation for the body.
