Everything about The Retinal Pigment Epithelium totally explained
The
retinal pigment epithelium (
RPE) is the
pigmented 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.
Appearance
The RPE is composed of a single layer of hexagonal
cells that are densely packed with pigment granules.
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
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's also involved in the
vitamin A cycle where it
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.
Further Information
Get more info on 'Retinal Pigment Epithelium'.
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