Ocular: RPE Flashcards
The RPE is contingent with what cell layer of the ciliary body?
Pigmented ciliary epithelium
What type of cells are in the RPE?
Monolayer of pigmented cells
The pigmented cells are located between what two things?
Choriocapillaris and outersegments photoreceptors
What surrounds the light-sensitive outer segments?
Long apical microvilli
The apical membrane cells of the RPE face what segment?
Photoreceptor outer segments
What does the basalateral membrane face?
Bruch’s membrane
What are the five layers of Bruch’s membrane?
Inner to outer:
-BM of RPE
-inner collagenous layer
-elastic layer
-outer collagenous layer
-BM of choriocapillaries
From what layer of the optic cup does the RPE differentiate?
The outer layer of the optic cup
RPE cell density is greatest in what region?
Fovea
How many cells in the RPE do not have regenerative capacity?
4-6 million cells
What do RPE cells face?
30-40 photoreceptor outer segments
The apex of RPE faces what?
The apex of the photoreceptor outer segment
What the functions of the RPE?
-absorption of light energy
-protection against photooxidation
-transepithelial transport
-producing important factors
-involved in visual cycle
-phagocytosis
How is light energy absorbed by the RPE? General and blue light
General light- melanin in RPE
blue light- lutein and zeaxantnin in photoreceptors and RPE
What are the non-enzymatic antioxidants?
lutein and zeaxanthin
What are the enzymatic antioxidants?
Superoxide dismutase and catalase
Why is the RPE important for transepithelial transport?
RPE transports nutrients and metabolic end products between the choroid and photoreceptors
How is water removed from the apical side (photoreceptors)?
Water conducting aquaporin membrane channels
What is the importance of the Cl- Channels?
Transport of water is driven by an active transport of Cl-
What is the importance of the Na+/K+ ATPase pumps on the apical side of the RPE cells?
Helps regulate extracellular potassium levels and fluid fluxes that contribute to the adhesion of the neurosensory retina
How is lactic acid removed from the retina?
-removed from apical side
-transport of lactic acid requires tight regulation of pH in sub retinal space
How is glucose transported across the RPE
GLUT1 and GLUT3 transporters
What is the importance of Pigment epithelium-derived factor (PEDF) secretion by the RPE?
-Inhibits endothelial cell proliferation
-stabilizes the endothelium of the choriocapillaries
-antiangiogenic factor
What is the importance of vascular endothelial growth factor (VEGF) secretion by the RPE?
-secreted in low concentration in the healthy eye bold text
-prevents endothelial cell apoptosis
-stabilizes the endothelium of the choriocapillaries
What is the most severe complication of age-related macular degeneration?
Choroidal neovascularization
What is choroidal neovascularization?
When RPE cells secrete VEGF at a higher concentration compared with RPE cells in non-neovascularization eyes
What is the importance of ciliary neurotrophic factor(CNTF)?
Protects photoreceptors from dying
What is the importance of tissue inhibitory matrix metalloproteinases (TIMP)?
Stabilizes extracellular matrix and prevents neovascularization
Overall, CNTF and TIMP are for..
Supporting the surrounding tissues
What are Drusen?
Hydrophobic material deposited by the RPE into the inner collagenous layer of Bruch’s membrane.
What do Drusen do?
Impede flow of nutrients into the retina and removal of metabolic waste from retina
Where are the Drusen deposited?
Inner collagenous layer of Bruch’s membrane
(Seems important so i put twice for good measure)
(If its not on block ill kms)
Drusens’ affects on the retina increase risk for what eye disease?
Increase risk of dry form age-related macular degeneration
What space is created by the apex to apex orientation of the RPE and photoreceptors?
Subretinal space
What is located in the subretinal space?
Interphotoreceptor matrix
What does the interphotoreceptor matrix control?
Trafficking of nutrients
Where are the Na+/K+ ATPase pumps located?
Apical membrane of RPE
What do the NA+/K+ ATPase pumps do?
They regulate fluxes to keep thee sensory retina adhered to RPE
What is located on the lateral membrane of the RPE and what do they form?
Tight junctions that form the outer blood retina barrier
What do the basal enfolding of the RPE do?
Increase surface area for cell absorption and secretion
apical microvilli function
Aids adhesion, phagocytosis, increased surface area for metabolic exchange
Lysosomes function
Contain hydrologic enzymes which digest photoreceptors
Junctional complex and terminal bar function
Component of blood-retinal barrier and ensures cell-cell adhesion
Phagosomes
Contain phagocytosed photoreceptor segments
Melanin granules function
Absorb excess visible light and UV. Reduces free-radical damage
Lipofusion
Ageing pigment , residual bodies from phagocytosis activity
Golgi apparatus function
Secretion and sulphation of GAGs
Basal enfoldings function
Increased absorptive surface
Rough and smooth endoplasmic reticulum function
Protein and lipid synthesis
Mitochondria function
Large numbers indicate active ‘pumping’ epithelium
The classical visual cycle involves the cycling of _______ between the rod outer segments and the RPE
11-cis-retinal
Reduction of _______ into ______ occurs in the outer segments of the photoreceptors
All-trans-retinal into all-trans-retinol
Reisomerization of _________ into _______ occurs in the RPE
All-trans-retinol into 11-cis-retinal
Retinitis pigmentosa is a result of
A mutation in the rhodopsin that cusses the rods to die off
