Flashcards in RPE Deck (79):
How is the RPE and photoreceptor outer segment aligned?
apex to apex
What is in the neural retina?
photoreceptors, bipolar, ganglion, horizontal and amacrine cells
Where is the ocular ventricle?
The potential space between the RPE and POS
After lens induction begins, the _____ _____ collapses back onto itself. The inner invagination becomes the _______ while the outer part becomes the _______
After lens induction begins, the *optic vesicle* collapses back onto itself. The inner invagination becomes the *neural retina* while the outer part becomes the *RPE*
The basement membrane of the RPE becomes ____ ____ during development. The basement of the neural retina becomes the ____ ____ ____
The basement membrane of the RPE becomes *Bruch's membrane* during development. The basement of the neural retina becomes the *inner limiting membrane*
Where would you find microvilli on the RPE?
the apical portion. Microvilli envelope the photoreceptors
The epithelial cells of the Blood Retinal barrier are bound together by _____ _____ and divide the cells into apical halves that face the _______ and basal halves that face the ______
The epithelial cells of the Blood Retinal barrier are bound together by *tight junctions* and divide the cells into apical halves that face the *receptors* and basal halves that face the *choroid*
What gives the RPE its black appearance?
What is proliferative vitreoretinopathy?
Pigment granules separate from the RPE as free cells and appear as "tobacco dust" in the vitreous. Cells then settle and form contractile fibrocellular membranes
What part of the retina uses the most energy?
The outer segments
Photoreceptor survival depends on having _____ and _____ in large quantities
blood and glucose
What are the four extreme properties that the choroid has developed to meet the demands of the photoreceptors?
1. High permeability
2. High throughput of blood - more blood faster
3. High oxygen levels
4. No auto-regulation
Name the two problems created by the thin and sparse central retinal circulation (made necessary since it lies in the path of light)
1. Very little oxygen reserve
2. Small vessel diameter
What are the five functions of the RPE? (RPEAM)
Photoreceptor renewal and light absorption
Environment protection against superoxides
A... Vitamin A metabolism and storage
What are the two aspects of the blood-retinal barrier?
1. Tight junctions of the endothelial cells of the CRC
2. Tight junctions of the RPE keeping blood out of the retina
The fenestrated choriocapillaries permit leakage of _______
Protein concentration in front of the RPE is ____ while the concentration in the ECS behind the RPE is ____
Protein concentration in front of the RPE is *low* while the concentration in the ECS behind the RPE is *high*
The RPE can absorb up to ___% of the aqueous secretion in a day
What are the factors preventing RPE/retina detachment?
1. Oncotic fluid gradient
2. Finger-like folds of the RPE
3. Interphotoreceptor matrix
Due to the high membrane fluidity required by the retina, the ____ bonds of the _____ _____ _____ make the retina highly susceptible to superoxide attack.
Due to the high membrane fluidity required by the retina, the *double* bonds of the *unsaturated fatty acids* make the retina highly susceptible to superoxide attack.
Hurler's syndrome is the buildup of _____ molecules due to an improperly functioning degrading _____
Hurler's syndrome is the buildup of *GAG* molecules due to an improperly functioning degrading *enzyme*
Photoreceptors are degraded by _____ and ____
Photoreceptors are degraded by *phagocytosis* and *autophagy*
A single RPE cells is responsible for phagocytosing ____ or more rods
Self-digestion by a cell through the action of enzymes of the same cell
What are the two patterns of photoreceptor replacement?
1. Membrane replacement
2. Molecular replacement
All structures in the rod turnover during membrane replacement except for ____
What two molecules are replaced independent of the discs in rods?
transducin and PDE
Where would the disc accumulate if photoreceptor renewal did not take place?
Phagocytosis of the photoreceptor outer segment is carried out by the ____
In order to digest the outer segment portion of a photoreceptor, a _____ fuses with the ____ ____.
In order to digest the outer segment portion of a photoreceptor, a *lysosome* fuses with the *RPE phagosome*
In embryogenesis up till 6 months, growth of photoreceptors is ______ than phagocytosis. From Age 6 months until adulthood, growth is ______ to phagocytosis. Disease is observed when growth is ______ than phagocytosis.
In embryogenesis up till 6 months, growth of photoreceptors is *greater* than phagocytosis. From Age 6 months until adulthood, growth is *equal* to phagocytosis. Disease is observed when growth is *less* than phagocytosis.
What can radioautography do?
Allows the researcher to follow the synthesis of a molecule by administrating a "pulse" of radiolabeled molecule into the molecule.
A radiolabeled molecule is referred to as ____
An unlabeled molecule seen during radioautography is referred to as _____
Photoreceptor renewal is _______ in cones than in rods
What do the proteins incisin and peripherin do in photoreceptors?
control the spacing of the discs
Where are polysaccharides found in a photoreceptor?
Between the discs. Acts as a cushion
The label in radioautography is found in a lipid-surrounded vesicle known as a _______
Rods are phagocytosed 1.5 hours after _____ and the cones are phaocytosed 1.5 hours after _____
Rods are phagocytosed 1.5 hours after *dawn* and the cones are phaocytosed 1.5 hours after *nightfall*
The circadian rhythm runs on a ___ hour cycle
True / False. Seeing and circadian control rely on the same receptor
Constant light results in the ______ of the outer segments while constant darkness results in _____ of the outer segments
Constant light results in the *shortening* of the outer segments while constant darkness results in *elongation* of the outer segments
What two methods has the cornea developed to act again oxidation by superoxides?
Chemical mechanism - superoxide dismutase
Anatomical mechanism - replacement of tissue
Oxidation takes place across what type of bond?
Why can't the lens replace its own tissue?
Cells are sloughed off towards the center
Shorter wavelength light is ______ destructive than longer wavelength light
Why is the retina the weakest tissue of the body?
Retina has highly fluid membranes
Macular pigments surround the macula and absorb _____ light in order to fight off free radicals.
The lens protects the retina by absorbing most of the incoming _____ light
Superoxides can be broken down to hydrogen peroxide and oxygen in the presence of ____, ____, ___, and _____ ______
Zn, Cu, Mn, and superoxide dismutase
Hydrogen peroxide may revert back to superoxide in the presence of ____
The Glutathione peroxidase pathway (the predominant retinal pathway) requires ____
As lipids become crosslinked, the super destructive element ________ is kicked out
Vitamins __ and __ are used to get rid of malonaldehyde
Vitamins C and E
When lipofuscin accumulates in the RPE, it becomes _____
Early accumulation of lipfuscin is seen in _____ and _____
Stargardt's and ARMD
Each RPE cell ingests more than any other phagocytic cell at __% of its own volume
11-cis-retinal + aporhodopsin -> ____ + _____
Rhodopsin + water
When exposed to light, rhodopsin breaks down into ______ + ______
aporhodopsin + all-trans-retinal
Humans typically begin with _______ photoreceptors
Retinal detachment = starvation due to a lack of ____ and ____
oxygen and glucose
______ _____ is the basement membrane of the RPE
What happens when Bruch's membrane is stretched?
Fatty acid deficiency in the choroid results in the inability to delivery ____ _ to the retina. This may lead to ____ ____
Vitamin A. Night blindness
_____ ____ is a generice name for a group of inherited disorders that cause progressive loss of photoreceptor and RPE function
Retinitis Pigmentosa (RP)
RP prevalence is about
Damage to the ___ is predominant in RP
In the oxygen toxicity hypothesis: as the outer segments are lost, oxygen use by the ____ diminishes and the ___ ___ is flooded with oxygen.
In the oxygen toxicity hypothesis: as the outer segments are lost, oxygen use by the *photoreceptors* diminishes and the *outer retina* is flooded with oxygen.
photoreceptors that survive oxygen toxicity are damaged and upregulate expression of _____ _____ which slows degeneration
What are the two types of ARMD?
dry and wet
In Dry ARMD, drusen appears which can either be ____, ____, or _____
soft (acute), hard (chronic), or calcified (under repair)
Why does drusen accumulate in the macula more than the fovea?
the fovea is protected by pigment
Accumulation of Drusen can lead to
How does Wet ARMD differ from Dry ARMD?
neovascularization in Wet ARMD
Aging changes may cause _____ blood flow
What transport mechanisms are used to pump ions in and out of the RPE?
Most potassium in the retina exist through the ____ ____
HCO exits the retina through the ____ _____ in the RPE choroidal membrane