Epidermis (skin)

Epidermis
Histologic image of epidermis, delimited by white bar.
Histologic image detailing epidermal layers. Stratum corneum appears more compact in this image than above because of different sample preparation.
Details
Identifiers
Latin	Epidermis
Code	TH H3.12.00.1.01001
TA	A16.0.00.009
FMA	70596
Anatomical terminology []

The epidermis is the outer (epi in Greek meaning "over" or "upon") of the two layers that make up the skin (or cutis), the inner layer being the dermis. It provides a barrier to infection from environmental pathogens and regulates the amount of water released from the body into the atmosphere through transepidermal water loss (TEWL). The outermost part of the epidermis is composed of stratified layers of flattened cells, that overlies a basal layer (stratum basale) composed of columnar cells arranged perpendicularly.

The epidermis has no blood supply and is nourished almost exclusively by diffused oxygen from the surrounding air. It is 95% keratinocytes (proliferating basal and differentiated suprabasal) but also contains melanocytes, Langerhans cells, Merkel cells, and inflammatory cells. Rete ridges ("rete tips") are epidermal thickenings that extend downward between dermal papillae.Blood capillaries are found beneath the epidermis, and are linked to an arteriole and a venule..

The epidermis is composed of 4 or 5 layers depending on the region of skin being considered. Those layers in descending order are:

The term Malpighian layer (stratum malpighi) is usually defined as both the stratum basale and stratum spinosum.