ABSTRACT
The skin is a complex organ with many important functions. It serves as a mechanical barrier, participates in thermoregulation, has immunological activity, protects against ultraviolet effects, and balances water loss. To fulfill all these functions, the skin has multiple cellular components and non-cellular structures. Skin is composed of an epithelial layer of ectodermal
origin, the epidermis, a layer of connective tissue of mesodermal origin, the dermis, and loose connective tissue with fat, the hypodermis. The irregular junction of the dermis and epidermis is called the dermoepidermal junction (Figure 2.1). It is created by projections of the dermis called papillae, which interdigitate with invaginations of the epidermis called epidermal ridges. Epidermal appendages include hairs, nails, and sebaceous and sweat glands.
