The skin is made up of an epithelium (epithelial cells) called the epidermis, a connective tissue (elastic and collagen cells) called the dermis and an adipose tissue called subcutaneous.
The skin appendages (nails, hair and hair), vessels and nerves are contained in the dermis and subcutaneous.
The basal layer is adjacent to the dermis and consists of a single layer of cylindrical keratinocytes. They represent the germ cells of the epidermis, on whose division the continuous renewal of the epithelium depends. Interposed between the basal keratinocytes are the melanocytes, cells whose main function is to produce and secrete melanin, then transferring it to the keratinocytes. They are more numerous in the photo-exposed areas such as the face and less in the trunk.
Above the spiny cells, as they mature and begin to keratinize, we find the granular layer, which is usually 1 or 2 cells thick.
The shiny layer is located above the granular but is clearly evident only in some places, especially the palms of the hands and the soles of the feet.
The superficial layer of the epidermis is the stratum corneum, usually of a thickness equivalent to 3-4 cells. In it, the cells are mainly composed of keratin filaments and aggregate giving it a "woven basket" appearance. In areas subjected to pressure or trauma is thickened and thickened.
The dermis is composed of two parts, the papillary, located below the epidermis, and the reticular, located between the papillary and hypodermis. It contains collagen (which allows it a considerable resistance to traction), elastic fibers (which give it a "reversible extensibility), glycosaminoglycans (which give it hydration and firmness) and the skin appendages, ie the hair follicles and associated structures (sebaceous glands and erector hair muscles).
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