Retinal pigment epithelium
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{{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]]