The skin is the organ that protects and covers the surface of the body and binds, seamless, with the mucous membranes of the various channels in various body orifices. The skin forms a protective barrier against the action of physical, chemical or bacterial agents on deeper tissues, and contains special bodies often grouped to detect the different sensations like sense of touch, temperature and pain. It plays an important role in maintaining body temperature thanks to the action of the sweat glands and blood capillaries. In regulating body temperature involved the 4.5 m of capillaries contained in each 6.5 cm2 skin.I
When the body temperature rises heat energy or heat is lost because the vascular dilatation occurs and blood flow to the skin surface increases. When the temperature is low, the blood vessels constrict to reduce the blood flow and the consequent heat loss through the skin. Each square centimeter of skin also contains hundreds of sweat glands that are controlled by a heat regulation center located in the brain.I
These glands secrete moisture evaporates, it cools the body surface and helps maintain normal body temperature. In this case, the skin acts as a secretory organ. The skin is elastic and, except in some areas such as the palms of the hands, soles of the feet and ears, is weakly attached to the underlying tissues. The skin color varies with the amount of a pigment called melanin, which is deposited in skin cells, which is determined by inheritance and by exposure to sunlight. Color also varies in some diseases from differences in pigmentation, as in Addison's disease, or because the blood transports pigmented substances deposited on the skin.I
In certain regions of the body the outer layers of the skin are modified to form the hair and nails. The skin thickness varies between 0.5 mm on the eyelids and 4 mm or more in the palms of the hands and soles of the feet. The skin consists of two different layers. The outer layer called epidermis or cuticle. It has several cells thick and has an outer layer of dead cells that are constantly removed from the skin surface and replaced by other cells formed in a basal cell layer, called the stratum germinativum and containing cuboidal cells in constant division.I
The cells generated in it will flatten as they rise to the surface, where they are eliminated; also it contains melanocytes or cells containing melanin pigment in varying amounts. The inner layer is the dermis. It consists of a network of collagen and elastic fibers capillary blood, nerve, fatty lobes and the base of hair follicles and sweat glands. The interface between dermis and epidermis is very irregular and consists of a succession of papillae, or finger-like projections, which are smaller in areas where the skin is thin, and longer in the skin of the palms and the soles of the feet.I
In these areas, the papillae are associated with elevations of the epidermis producing undulations used for identifying fingerprints. Each disc contains either a capillary loop of blood vessels or specialized nerve ending. Vascular loops provide nutrients to the epidermis and outnumber neural buds in a ratio of four to one.I
The sweat glands are distributed throughout the body. They are numerous in the palms of the hands and soles of the feet, but quite rare in the skin of the back. Each gland consists of a series of tubular coils positioned in the subcutaneous tissue, and a conduit extending through the dermis and form a helically wound in the epidermis. The sebaceous glands are sac and secrete sebum that lubricates and softens the skin. They open into the hair follicles to close below the epidermis.