Epidermis

The epidermis is the outermost of the three layers that comprise the <a href="/facts/Skin/4havlLzG">skin</a>, the inner layers being the <a href="/facts/Dermis/WAm7Fd6P">dermis</a> and <a href="/facts/Subcutaneous_tissue/EPYjXN3G">hypodermis</a>. The epidermal layer provides a barrier to <a href="/facts/Infection/182XrncP">infection</a> from environmental <a href="/facts/Pathogens/axMXtV1M">pathogens</a> and regulates the amount of water released from the body into the <a href="/facts/Atmosphere/oUpLaGRF">atmosphere</a> through <a href="/facts/Transepidermal_water_loss/QaqAk6l9">transepidermal water loss</a>.
The epidermis is composed of <a href="/facts/Stratified_squamous_epithelium/RLlp5jnr">multiple layers of flattened cells</a> that overlie a base layer (<a href="/facts/Stratum_basale/4UwmB3Qm">stratum basale</a>) composed of <a href="/facts/Epithelium/ecKHcHC3">columnar cells</a> arranged perpendicularly. The layers of cells develop from <a href="/facts/Stem_cell/qgB9dFrI">stem cells</a> in the basal layer. The thickness of the epidermis varies from 31.2μm for the <a href="/facts/Penis/s9zpC49k">penis</a> to 596.6μm for the <a href="/facts/Sole_(foot)/v6sV8LDE">sole of the foot</a> with most being roughly 90μm. Thickness does not vary between the sexes but becomes thinner with age. The human epidermis is an example of <a href="/facts/Epithelium/ecKHcHC3">epithelium</a>, particularly a <a href="/facts/Stratified_squamous_epithelium/RLlp5jnr">stratified squamous epithelium</a>.
The word epidermis is derived through Latin from <a href="/facts/Ancient_Greek_language/LIK7NlUh">Ancient Greek</a> epidermis, itself from <a href="/facts/Ancient_Greek_language/LIK7NlUh">Ancient Greek</a> epi 'over, upon' and from <a href="/facts/Ancient_Greek_language/LIK7NlUh">Ancient Greek</a> derma 'skin'. Something related to or part of the epidermis is termed epidermal.

Epidermis open-in-new

Epidermis