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Lecture 21: RPE
RPE
| Question | Answer |
|---|---|
| What is the RPE? | monolayer of polarized CUBOIDAL epithelial cells. it separates the photoreceptors from their blood supply (choroidal vasculature) |
| What are the functions of the RPE? | 1.ABSORPTION of stray light to enhance visual acuity 2.PROTECTION against toxic and oxidative damage 3.FORMATION of the blood- retina- barrier 4.SELECTIVE TRANSPORT of substances to/from neural retina 5.ELIMINATION of metabolic waste 6. PROCESSING of vit |
| What is the RPE composed of? | 4 to 6 million cells in a hexagonal pattern |
| What is the cell density of RPE? | GREATEST: fovea LOWEST: periphery |
| What is the RPE cell responsible for? | they face ~30-40 photoreceptors. PHAGOCYTIZE shed discs of photoreceptor outer segments on a daily basis |
| What is the RPE continuous with? | pigmented epithelium of the ciliary body |
| How are the neural retina and RPE arranged? | apex- to- apex intimate relationship between APICAL OUTER SEGMENTS of the photoreceptors and the APICAL MICROVILLI of the RPE cells. |
| What is the subretinal space? | potential space seaparating the RPE from photoreceptor |
| how is the RPE situated? | APEX: inward (towards vitreous) BASAL: faces outward (towards schlera) |
| Where is the BM of the RPE located? | inner most layer of Bruch's membrane of choroid |
| At the apical surface of the RPE, how does it connect with the rod outer segments? | extends numerous microvilli into the space between RPE from photoreceptors (subretinal space) that interlock with the rod outer segments |
| What is the interphotoreceptor matrix (IPM)? | located between the apical membrane and photoreceptors. it keeps the APICAL MICROVILLI and PHOTORECEPTOR OUTER SEGMENTS bound together, but no junctional attachments occur. it also exchanges metabolites and interactions between the photoreceptors and RPE |
| What is the purpose of the microvilli? | they phagocytize the discs of the photoreceptor outer segments and can be seen in the cytoplasm of the RPE as phagosomes |
| what happens to the phagosomes by INTRAcellular enzymes?? | they are gradually digested by intracellular enxymes and their end products are 1. deposited on Bruch's membrane (drusen) or 2. stay within the cell as lipofuscin grandues |
| Does the lipofuscin grandules increase or decrease with age? | increase |
| what time of day are the rods and cones shed? | RODS: early morning CONES: end of the day |
| how long does it take for a complete turnover of the photoreceptor outer segments? | once every 8-13 days |
| Why is the RPE cell so unique? | in the APICAL membrane: NA-K-ATPase. but other transport epithelia have this system in the basolateral PM. this system helps regulate fluid fluzes that contribute to the adhesion of neurosensory retina to the RPE |
| What is special about the lateral membrane of RPE? | zonular occluden is more apical in this membrane. it is the junction that destroys the space between adjacent RPE cells that form blood- retina- barriers. |
| What is special about the basal membrane of the RPE? | highly complex with infoldings to about 1micrometer into the cytoplasm of the cell. the infolding incrase the SA of the cell for ABSORPTION and SECRETION (transport function) |
| Where does drusen deposit? | between the BM of the RPE and inner collagenous layer of the colloid |
| The deposits of metabolic waste on Bruch's membrane make it? | hydrophobic, which causes a reduction in water permeability |
Created by:
dyoungee
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