One of the main functions of human skin is to act as a protective barrier against the external environment. Subcutaneous fat and dermal connective tissue help cushion and disperse mechanical trauma, but the actual barrier principally depends on the integrity of the epidermis, including the stratum corneum, as well as a complex network of adhesive junctions that link adjacent keratinocytes to one another as well as basal keratinocytes to the underlying dermis.