Editing Epidermis (section)

{{short description|Outermost of the three layers that make up the skin}}
{{about|skin in mammals}}
{{Infobox microanatomy
| Name        = Epidermis
| Latin       = epidermis
| Image       = Epidermis-delimited.JPG
| Caption     = [[Histology|Microscopic]] image of the epidermis, which constitutes the outer layer of skin, shown here by the white bar
| Image2      = Epidermal layers.png
| Caption2    = Microscopic image showing the layers of the epidermis. The ''stratum corneum'' appears more compact in this image than above because of different sample preparation.
| Precursor   =
| System      = [[Integumentary system]]
| PartOf = [[Skin]]
}}

The '''epidermis''' is the outermost of the three layers that comprise the [[skin]], the inner layers being the [[dermis]] and [[Subcutaneous tissue|hypodermis]].<ref>{{Cite book|title=Wheater's functional histology a text and colour atlas| vauthors = Young B |publisher=Elsevier|year=2014|isbn=9780702047473|pages=160 & 175}}</ref> The epidermal layer provides a barrier to [[infection]] from environmental [[pathogens]]<ref name="Lookingbill">{{cite book | vauthors = Marks JG, Miller J | title = Lookingbill and Marks' Principles of Dermatology | edition = 4th | publisher = Elsevier | year = 2006 | pages = 1–7 | isbn = 978-1-4160-3185-7 }}</ref> and regulates the amount of water released from the body into the [[atmosphere]] through [[transepidermal water loss]].<ref name="Proksch">{{cite journal | vauthors = Proksch E, Brandner JM, Jensen JM | title = The skin: an indispensable barrier | journal = Experimental Dermatology | volume = 17 | issue = 12 | pages = 1063–1072 | date = December 2008 | pmid = 19043850 | doi = 10.1111/j.1600-0625.2008.00786.x | s2cid = 31353914 }}</ref>

The epidermis is composed of [[stratified squamous epithelium|multiple layers of flattened cells]]<ref name="Rooks">{{cite book | vauthors = McGrath JA, Eady RA, Pope FM | title = Rook's Textbook of Dermatology | year = 2004 | edition = 7th | publisher = Blackwell Publishing | isbn = 978-0-632-06429-8 | pages = 3.1–3.6 }}</ref> that overlie a base layer ([[stratum basale]]) composed of [[Epithelium#Cell types|columnar cells]] arranged perpendicularly. The layers of cells develop from [[stem cell]]s in the basal layer.  The thickness of the epidermis varies from 31.2μm for the [[penis]] to 596.6μm for the [[Sole (foot)|sole of the foot]] with most being roughly 90μm. Thickness does  not vary between the sexes but becomes thinner with age.<ref name="Lintzeri Karimian Blume‐Peytavi Kottner 2022 pp. 1191–1200">{{cite journal |last1=Lintzeri |first1=D.A. |last2=Karimian |first2=N. |last3=Blume-Peytavi |first3=U. |last4=Kottner |first4=J. |date=2022 |title=Epidermal thickness in healthy humans: a systematic review and meta-analysis |journal=Journal of the European Academy of Dermatology and Venereology |volume=36 |issue=8 |pages=1191–1200 |doi=10.1111/jdv.18123 |issn=0926-9959|doi-access=free |pmid=35366353 }}</ref> The human epidermis is an example of [[epithelium]], particularly a [[stratified squamous epithelium]].

The word epidermis is derived through Latin {{ety|grc|epidermis}}, itself {{ety|grc|epi|over, upon}} and {{ety|grc|derma|skin}}.  Something related to or part of the epidermis is termed epidermal.