FIGURE 1.

Human skin. The outermost layer of human skin is built by stratified epidermis. The bottom layer is called stratum basale and contains proliferating basal keratinocytes that are anchored to the basement membrane. While differentiating, they migrate from the stratum basale, through the stratum spinosum, stratum granulosum, and the stratum lucidum (not shown) to the stratum corneum. The vascularized dermis can further be separated into the upper papillary and the lower reticular dermis. Skin appendages, such as hair follicles, are embedded in the dermis and reach through the epidermis, whereas other appendages reside mostly in the dermis. The innermost skin layer is called hypodermis and is built by fat storing adipocytes. Note that not all skin appendages, and skin cells are shown.