Retinal pigment epithelium 5307111 223647274 2008-07-05T01:56:32Z Lightbot 7178666 Units/dates/other {{Infobox Anatomy | Name = Retinal pigment epithelium | Latin = p. pigmentosa retinae | GraySubject = 225 | GrayPage = 1016 | Image = Gray881.png | Caption = Section of [[retina]]. (Pigmented layer labeled at bottom right.) | Image2 = Gray882.png | Caption2 = Plan of retinal neurons. (Pigmented layer labeled at bottom right.) | System = | Precursor = | MeshName = | MeshNumber = | DorlandsPre = p_07 | DorlandsSuf = 12617535 | }} The '''retinal pigment epithelium''' ('''RPE''') is the [[pigment]]ed cell layer just outside the neurosensory [[retina]] that nourishes retinal visual cells, and is firmly attached to the underlying [[choroid]] and overlying retinal visual cells.<ref name="Cassin">{{cite book |author=Cassin, B. and Solomon, S. |title=Dictionary of eye terminology |publisher=Triad Pub. Co |location=Gainesville, Fla |year=2001 |pages= |isbn=0-937404-63-2 |oclc= |doi=}}</ref><ref>Boyer MM, Poulsen GL, Nork TM. "Relative contributions of the neurosensory retina and retinal pigment epithelium to macular hypofluorescence." Arch Ophthalmol. 2000 Jan;118(1):27-31. PMID 10636410.</ref> ==History== [[Image:Calf-Eye-Posterior-With-Retina-Detached-2005-Oct-13.jpg|thumb|right|Choroid dissected from a calf's eye, showing black RPE and iridescent blue tapetum lucidum]] The RPE was known in the 18th and 19th centuries as the '''pigmentum nigrum''', referring to the observation that the RPE is dark (black in many animals, brown in humans); and as the '''tapetum nigrum''', referring to the observation that in animals with a [[tapetum lucidum]], in the region of the tapetum lucidum the RPE is not pigmented.<ref>{{cite book |author=Coscas, Gabriel and Felice Cardillo Piccolino |title=Retinal Pigment Epithelium and Macular Diseases |publisher=Springer |location= |year=1998 |pages= |isbn=0792351444 |oclc= |doi=}}</ref> ==Anatomy== The RPE is composed of a single layer of hexagonal [[cell (biology)|cell]]s that are densely packed with pigment granules.<ref name="Cassin"/> When viewed from the outer surface, these cells are smooth and hexagonal in shape. When seen in section, each cell consists of an outer non-pigmented part containing a large oval [[cell nucleus|nucleus]] and an inner pigmented portion which extends as a series of straight thread-like processes between the rods, this being especially the case when the eye is exposed to light. ==Function== The retinal pigment epithelium is involved in the [[phagocytosis]] of the outer segment of photoreceptor cells and it is also involved in the [[vitamin A]] cycle where it [[Isomerisation|isomerizes]] all [[trans retinol]] to [[11-cis retinal]]. The retinal pigment epithelium also serves as the limiting transport factor that maintains the retinal environment by supplying small molecules such as amina acid, [[ascorbic acid]] and D-glucose while remaining a tight barrier to choroidal blood borne substances. [[Homeostasis]] of the ionic environment is maintained by a delicate transport exchange system. ==Pathology== In the eyes of [[albinos]], the cells of this layer contain no pigment. Dysfunction of the RPE is found in [[Age-Related Macular Degeneration]] and [[Retinitis Pigmentosa]]. ==References== {{reflist}} ==See also== *[[Bruch's membrane]] *[[Drusen]] ==External links== *{{MeshName|pigment+epithelium+of+eye}} * {{BUHistology|07902loa}} * {{KansasHistology|eye_ear|eye11}} {{Gray's}} {{Retina}} [[Category:Eye]] {{eye-stub}} [[ru:Пигментный эпителий сетчатки]]