The largest and probably one of the most important organs in the human body is its outer covering. Without it everything currently inside the body would fall off or simply be exposed to the elements of the outside world and left at the mercy of bacteria and infections floating in the air. The answer to this question is a double layer of covering called leather. It is also normally covered in hair (in some places such as the head) and nails at the ends of the fingers and toes. Collectively these linings are classified as the integumentary system. Although only a couple of millimeters thick, skin is made up of two layers, the first of which is the outer layer called the epidermis. The epidermis is a constantly reproducing layer of cells that protects the underlying layer, the dermis, from various environmental exposures such as UV light, bacteria, chemicals, disease and physical damage. The outer layer of the epidermis is composed of dead skin cells and is made up of the dermal layers of the skin that continually grow and form the epidermis. By cleansing the epidermis, sebaceous excretions (oils and waxes naturally produced by the dermis) any antigens on its surface are removed and thus prevented from entering the dermis and subsequent internal cells of the body. Exocrine glands within the dermis secrete these oils and transmit them into the epidermis to keep it hydrated. The skin is denser in some parts of the body than others, such as the palms of the hands and soles of the feet. As the epidermal layers shed, they are replaced by the underlying dermal layers as these are simultaneously replaced by new dermal cells. The part of the epidermis closest to the dermis houses the lamina germanica……middle of paper……ps to control and regulate body temperature. Furthermore, within the hair follicles, a secretion called sebum is released which helps to coat the hair, keep it shiny and soft and at the same time acts as a fungicidal and bacterial barrier, as well as a certain level of impermeability for the skin. Nails are hard plates of cells derived from the same composition as the dermal layers of the skin but primarily hard keratin plates. They are constantly reproduced and grown away from the nail root to produce new nails. They grow from the underside of the skin into the dermal layer, invisible to the eye, and the visible part of the nail takes on the color of the underlying blood vessels and appears pink. This is located on the nail bed and the distal end of the nail, the white part, is the part of the free edge that we cut. Nails are the equivalent of an animal's claws, horns, and hooves.