Epidermis (skin) 915924 222382225 2008-06-29T01:38:55Z 71.53.162.107 /* Components */ [[Image:Skin.jpg|thumb|300px|Cross-section of all skin layers]] [[Image:HautFingerspitzeOCT.gif|thumb|300px|[[Optical coherence tomography]] tomogram of fingertip, depicting stratum corneum (~500µm thick) with stratum disjunctum on top and stratum lucidum (connection to stratum spinosum) in the middle. At the bottom superficial parts of the dermis. Sweatducts are clearly visible.]] '''Epidermis''' is the outermost layer of the [[skin]]. It forms the waterproof, protective wrap over the body's surface and is made up of stratified squamous [[epithelium]] with an underlying [[basal lamina]]. ==Components== What the epidermis looks like is avascular (contains no [[blood vessel]]s) and is nourished by [[diffusion]] from the [[dermis]]. The main type or the four principal types of cells which make up the epidermis are [[keratinocyte]]s, [[melanocyte]]s, [[Langerhans cell]]s and [[Merkels cell]]s. The outermost layer of epidermis consists of 25 to 30 layers of dead cells. The human skin is organised in distinct layers. Cells are born in the deep layers and migrate outward, flattening as they go, to form a protective barrier of dead cells at the surface (stratum corneum). The stratum corneum is a multi-layered brick and mortar like structure. It consists of lipid bilayers with alternating hydrophilic and hydrophobic areas. This is an efficient barrier against chemicals that are unsoluble in fat and against those which are unsoluble in water.<ref name=Benson2005> {{cite journal |author=Benson, Heather A. E. |title=Transdermal drug delivery: penetration enhancement techniques. |url= http://www.ncbi.nlm.nih.gov/pubmed/16305405 |journal=Curr Drug Deliv |volume=2 |issue=1 |pages=23-33 |year=2005 |pmid=16305405 |issn=}}</ref> To overcome this barrier is a challenge for the development of transdermally delivered drugs (like nicotine patches, topically applied pain relief). ==Sublayers== Epidermis is divided into the following 5 sublayers or strata, listed from the superficial to deep: * [[Stratum corneum]] * [[Stratum lucidum]] (not present in thin skin, only thick, hairless skin of palms & soles) * [[Stratum granulosum]] * [[Stratum spinosum]] * [[Stratum germinativum]] (also called "stratum basale") It is the deepest layer of the skin specifically the epidermis. The anatomical structure of it is composed of a single row of cuboidal or columnar keratinocytes. [[Mnemonic]]s used for remembering the layers of the skin (using "stratum basale" instead of "stratum germinativum"): * "'''C'''orn '''L'''overs '''G'''row '''S'''everal '''B'''ales" (from superficial to deep) * "'''C'''ome '''L'''ets '''G'''et '''S'''ome '''B'''eers" (from superficial to deep) * "'''C'''alifornians '''L'''ove '''G'''irls in '''S'''tring '''B'''ikinis" (from superficial to deep) * "'''B'''efore '''S'''igning, '''G'''et '''L'''egal '''C'''ounsel" (from deep to superficial) ==Additional images== <gallery> Image:Skinlayers.png|Section of epidermis. Image:Skinn_layer_drawing.jpg|Skin layers. Image:Spongiotic dermatitis (2) Dyshidrotic .JPG|Histopathological image of dyshidrotic dermatitis, showing focal spongiotic change in the epidermis. Image:HautAufbau.png|Schematics of internal human skin depicting its inner structure. Image:Gray942.png|The distribution of the bloodvessels in the skin of the sole of the foot. Image:Gray944.png|Cross section showing layers of epidermis. </gallery> ==External links== * {{BUHistology|08422loa}} - "Integument: thick skin" {{integumentary_system}} [[Category:Integumentary system|Epidermis]] [[ar:بشرة]] [[bg:Епидермис]] [[ca:Epidermis]] [[cs:Pokožka (živočichové)]] [[de:Epidermis (Wirbeltiere)]] [[eo:Epidermo]] [[fr:Épiderme (anatomie)]] [[hr:Epiderma]] [[it:Epidermide]] [[he:אפידרמיס]] [[lt:Epidermis]] [[ms:Lapisan epidermis]] [[nl:Epidermis]] [[ja:表皮]] [[pl:Naskórek]] [[ru:Эпидермис]] [[sk:Pokožka (anatómia)]] [[sr:Покожица]] [[fi:Orvaskesi]] [[sv:Överhuden]] [[th:หนังกำพร้า]] [[tr:Epidermis]] [[uk:Епідерма]] [[zh:表皮 (皮膚)]]