Stratum corneum 874247 210165728 2008-05-04T19:55:00Z Idioma-bot 2964546 robot Adding: [[ja:角質]] {{Infobox Anatomy | Name = Stratum corneum | Latin = stratum corneum epidermidis | GraySubject = 234 | GrayPage = 1064 | Image = Skinlayers.png | Caption = Section of epidermis. (Stratum corneum labeled at top left.) | Image2 = | Caption2 = | System = | Precursor = | MeshName = | MeshNumber = | DorlandsPre = s_25 | DorlandsSuf = 12761112 | }} The '''stratum corneum''' ("horny layer") is the outermost layer of the [[epidermis (skin)|epidermis]] (the outermost layer of the [[skin]]). It is composed mainly of dead [[cell (biology)|cell]]s that lack [[cell nucleus|nuclei]]. As these dead cells slough off, they are continuously replaced by new cells from the [[stratum germinativum]] (basale). In the human forearm, for example, about 1300 cells/cm<sup>2</sup>/hr are shed and commonly accumulate as house dust. This outer layer that is sloughed off is also known as the stratum dysjunction. Cells of the stratum corneum contain [[keratin]], a [[protein]] that helps keep the skin hydrated by preventing [[water]] [[evaporation]]. In addition, these cells can also [[absorption|absorb]] water, further aiding in hydration and explaining why humans and other animals experience [[wrinkle|wrinkling]] of the skin on the [[finger|fingers]] and [[toes]] (colloquially called "pruning") when immersed in water for prolonged periods. The thickness of the stratum corneum varies according to the amount of protection and/or grip required by a region of the body. For example, the [[hand]]s are typically used to grasp objects, requiring the palms to be covered with a thick stratum corneum. Similarly, the [[sole]] of the [[foot]] is prone to injury, and so it is protected with a thick stratum corneum layer. In general, the stratum corneum contains 15 to 20 layers of dead cells. The stratum corneum has a thickness between 10 and 40 μm. (=0.04mm) In [[reptile]]s, the stratum corneum is permanent, and is replaced only during times of rapid growth, in a process called [[ecdysis]] or [[moulting]]. The stratum corneum in reptiles contains [[beta-keratin]], which provides a much more-rigid skin layer. == External links == * {{LoyolaMedEd|medicine/dermatology/skinlsn/stcorn.htm}} * {{BUHistology|08422loa}} - "Integument: thick skin" {{integumentary_system}} [[Category:Integumentary system]] [[de:Epidermis (Wirbeltiere)#Stratum_corneum]] [[fr:Stratum corneum]] [[lt:Raginis sluoksnis]] [[nl:Hoornlaag]] [[ja:角質]] [[pl:Skóra właściwa]] [[fi:Marraskesi]]