topic 9 retina Flashcards
what is the retina, what is it bound by externally and internally? Where does the retina extend from? (Aka the firm attachments)
a thin transparent membrane
bound by Bruch’s membrane (externally) & vitreous (internally)
extends from the ora serrata to the optic nerve head
what are the 2 main segregations of the retina? how many layers are there altogether?
RPE (1 layer) and neurosensory retina (9layers)
there are 10 layers altogether
what is the RPE and the neural retina continuous of?
The RPE is continuous anteriorly with the outer pigmented epithelial layer of the cliary body
the neural retina is continuous with inner non-pigmented epithelium.
what is the subretinal space?
Potential space between neural retina and RPE
what is the main function of the neural retina?
converts light stimuli into information which is processed by the optic nerve and sent to the brain for interpretation.
describe the structure of the RPE (4 features) hint: where is it attached? Microvilli and pigments)
- single layer of columnar/cuboidal cells
- attached to Bruch’s membrane of the choroid
- apical surface is formed into microvilli
- contains melanin, lipofuscin
what are the 6 functions of the RPE?
- Absorbs stray light
- Provide pathway for metabolites to the receptors & remove waste products from receptors
- Give mechanical stability to the tips of receptors
- Forms part of the blood-retina barrier
- Phagocytosis of the outer segments/mebrane discs of the rods
- Metabolises and stores vitamin A
what are the 3 main types of neurons in the neural retina?
- photoreceptor cells (rods & cones)
- bipolar cells
- ganglion cells
what are the 9 layers of the neural retina? (outer to inner)
- PRL
- ELM
- ONL
- OPL
- INL
- IPL
- GCL
- NFL
- ILM
what are the 2 egs of neuroglial cells?
Muller cells and astrocytes.
They are NOT neurons, but are supporting cells.
what are the 5 regional variations in the retina? in terms of presence of rods and cones
ONH: no rods, no cones (blind spot)
Macula: has cones and rods
cones > rods
Fovea: has rods and cones
cones»_space; rods
foveola: only has cones, no rods
peripheral retina: has both rods and cones
rods > cones
what does the ONH comprise of? where does the ONH lie? Are there any photoreceptors here and what enters here?
Optic Nerve Head= Neural Rim + Optic Cup
3mm medial/nasal to the centre of the macula (fovea)
No photoreceptors, blind spot
Arteries enter and nerve fibres exit here
Nerve fibres exit through lamina cribossa and CRA pierces sheath of ON to enter
what is the neuroretinal rim? what is the optic cup?
pinkish area which contains the nerve fibers is the neuroretinal rim.
the centre is slightly depressed and is known as the optic cup.
what is the blood supply for the inner and outer retina?
Inner Retina: Supplied by the Central Retinal Artery (and Vein)
Outer Retina: photoreceptors and the RPE are supplied by the choriocapillaris underneath (branches of the ciliary arteries)
why is central retina thicker?
Central retina close to the fovea is considerably thicker (due to the increased packing density of photoreceptors, particularly the cones, and their associated bipolar and ganglion cells in central retina compared with peripheral retina).
