Lecture 10: RPE Flashcards by Makayla Shore

what are the 10 layers of the retina

Internal limiting membrane (ILM)
Nerve fiber layer (NFL)
Ganglion cell layer (GCL)
Inner plexiform layer (IPL)
Inner nuclear layer (INL)
Outer plexiform layer (OPL)
Outer nuclear layer (ONL)
External limiting membrane (ELM)
Photoreceptor layer (PR)
Retinal Pigmented epithelium (RPE)

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the RPE (10th layer of the retina) is what type of layer?

Monolayer of polarized cuboidal cells that separate photoreceptors from their underlying blood supply (choroid)

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what are the 6 RPE functions

Absorption of stray light
Protection against toxic and oxidative damage
Blood-retina-barrier
Selective transport of substances to and from the retina
Elimination of metabolic waste
Processing Vitamin A metabolites

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cell density is greatest where

fovea (~5000 cells/mm2)

peripherally (~2000 cells/mm2)

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Are RPE and PRs are arranged apex- to-apex or base to base? what is this due to… and what is the result of this?

RPE and PRs are arranged apex- to-apex due to embryoloigcal development. Thus, a potential space, the subretinal space, is located between them.

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what fills the subretinal space? what does it control?

Interphotreceptor matrix fills the space, is very strong, but no junctions. Controls trafficking of nutrients

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RPE basement membrane is innermost layer of what?

Bruch’s membrane

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RPE extends from

ora serrata (transitions from pigmented ciliary epithelium) to just before the optic disc

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what is at the apical end of the RPE projecting between the OS of PRs

microvilli

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Apical Membrane Specializations

Apical Na+/K+ ATPase pumps

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Each RPE cell faces how many PRs

30-40 PRs

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when do rods and cones shed?

Rod discs are shed in the early morning

* Cone discs are shed during the evening

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why is the RPE cell unique

it has Na+/K+ATPase pumps on its apical surface.

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why is a Na+/K+ATPase pumps on its apical surface of RPE needed?

To regulate fluxes to keep the sensory retina (PR) adhered to the RPE

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nutrient in

waste out

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RPE does what to PR discs?

RPE digests, and recycles PR discs

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what happens if the RPE can’t do its job?

If RPES can’t do its job it will dump the partially digested materials (hydrophobic) onto bruch’s membrane (DRUSEN), if stays within the cell

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Drusen =

lipofuscin (increases with age)

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what are the 10 ultrastructure features of the RPE

apical microvilli
lysosome
junctional complex and terminal bar
phagosomes
melanin granules
lipofuscin
golgi apparatus
basal infoldings
RER and SER
mitochondria

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Ultrastructure function: apical microvilli

aids adhesion, phagocytosis, increased SA for metabolic exchange

Ultrastructure function: lysosome

contains hydrolytic enzymes which digest PRs

Ultrastructure function: junctional complex and terminal bar

component of blood- retinal barrier and ensures cell-cell adhesion

Ultrastructure function: phagosomes

contains phagocytosed PR segments

Ultrastructure function: melanin granules

absorbs excess visibile light and UV – reduces free radical damage

Ultrastructure function: lipofuscin

'ageing pigment', residual bodies from phagocytotic activity

Ultrastructure function: golgi

secretion and sulphation of GAGs

Ultrastructure function: basal infoldings

increase surface area for cell absorption and secretion

Ultrastructure function: RER/SER

protein and lipid synthesis

Ultrastructure function: mitochondria

large numbers indicate active 'pumping' epithelium

Lateral membrane (specialization of RPE): tight junction

blood - retina - barrier

RPE: blood -retina- barrier has tight junctions between what two cells

* Tight junctions (zonulae occludentes) between the RPE cells * Tight junctions between the non-fenestrated endothelial cells of the retinal capillaries

TF: Retinitis pigmentosa (PR) is an autosomal recessive retinal dystrophy

F: An autosomal dominant retinal dystrophy

what is a progressive loss of RPE and PR function

Retinitis pigmentosa

RP Apoptosis:

rods and cones

Functional in peripheral retina

rods

functional in the Fovea

cones

"tunnel vision"

(RP) Bone-spicule pattern:

RPE degenerates | and pigment migrates and deposits around blood vessels

RP treatment:

• To slow down progression • High Doses of VitaminA (15000 IU/day) • DHA, Omega 3, Vit C 1000mg, Lutein, Zeaxanthine (no solid evidence)

Congenital hypertrophy of the retinal pigmented epithelium (CHRPE) lesions are typically

solitary, flat, well-demarcated, hyperpigmented lesions of the retina, seen in a grouped configuration like "bear tracks"

Both solitary lesions and "bear tracks" are

benign

multiple, bilateral lesions can be associated with Gardner's syndrome

an autosomal dominant disease which invariably results in colon cancer by the fifth decade of life

Retina:

window into CNS and Cardiovascular systems

retinal detachment (RD) usually separate at

RPE and PR | layer (as no intracellular junctions)

T/F: RPE remain attached to choroid and | can not be separated without difficulty

T: RPE remain attached to choroid and | can not be separated without difficulty

RD separates PR from their blood | supply, if not attached quickly what will happen to PR cells

if not attached quickly PR cells | will necrose and die

Argon laser is used to produce scar at | edges of RD to prevent

enlargement | and to reposition the layer

what can be used to reattach the retina and prevent fluid leakage in to breaks and subretinal space

``` Silicon oil (72% success rate) or gas temponade perfluropropane (87% success) ```