The epidermis, which is the outermost layer of mammalian skin, provides an essential barrier that is essential for maintenance of life. The epidermis is a stratified epithelium, which is maintained by the proliferation of epidermal stem cells (EPSCs) at the basal layer of the epidermis.
The epidermis is composed of the outermost layers of cells in the skin, “epi” in Greek meaning “over” or “upon”, which together with the dermis forms the cutis.
The epidermis is a stratified squamous epithelium,composed of proliferating basal and differentiated suprabasal keratinocytes which acts as the body's major barrier against an inhospitable environment, by preventing pathogens from entering, making the skin a natural barrier to infection.
It also regulates the amount of water released from the body into the atmosphere through transepidermal water loss (TEWL).
In humans, it is thinnest on the eyelids at 0.05 mm (0.0020 in) and thickest on the palms and soles at 1.5 mm (0.059 in).
It is ectodermal in origin.