POSTERIOR SEGMENT - Neurosensory Retina Flashcards
What is the structure of rod cones from RPE to vitreous?
Outer segment (transductive) –> inner segment (region for maintenance of cellular homeostasis) –> nuclear region (outer nuclear layers) –> transmissive region (outer plexiform/synaptic layer)
Which types of cells are present in the inner nuclear layer? (3)
(1) bipolar neurons
(2) horizontal cells
(3) amacrine cells
What is the difference between the outer segments of rods and cones ? (2)
RODS: cylindrical and contain rhodopsin pigment, made up of vitamin A (night blindness)
CONES: conical and contain iodopsin pigment (colour blindness)
What is the difference in numbers between rods and cones?
rods: 120 million
cones: 5 million
what is the maximum spectral sensitivity of the rod cells?
496nm
What are the main differences between rods and cones? (4)
- Rod discs are enclosed with a cell membrane
- Rod concentration higher in periphery
- Ratio of rod:cone is 20:1
- Peak sensitivity of rods is 496nm, cones is 420 (S), 530 (M) and 560 (L)
What is the most common location for midget ganglion cells and midget bipolar cells?
What is their synapse ratio with cones?
Where do they project to?
Fovea.
1:1 ratio with cones to allow high resolution of the fovea region.
project to the parvocelllular layers of the LGN (P cells)
Which cell is responsible for retinal scar tissue formation?
Astrocytes.
What is the function of muller cells?
the main glial cells of the retina which support in architectural and metabolic functions of the retina.
They contribute to the blood retinal barrier.
What is the structure of astrocytes?
What is the function of astrocytes?
Honeycomb/pattern formation cells peripendicular to the muller cells
Responsible for laying down scar tissue in injured or diseased retina
What is the structure and function of microglia cells?
highly specialised mononuclear phagocytic cells and are first line of defence against pathogen invasion.
What is the maximal spectral sensitivity of the rod?
496nm (blue-green light)
Where is the superficial capillary plexus of the retina located in?
the nerve fiber and ganglion cell layers, at the same level as the arterioles and major venules
Where is the deep capillary plexus of the retina located in?
between the inner nuclear layer and the outer plexiform layer.
Where is the avascular outer retina located in?
the FAZ - comprises the outer nuclear layer and photoreceptors
Where is the choriocapillaris layer located?
About 30um below the RPE/Bruch’s membrane
The retinal capillaries are surrounded by which type of cells? (3)
- Astrocyte foot processes
- Pericytes (contractile)
- Thick basal lamina
What is the flow rate of the retinal vessels? What layers do they supply?
High oxygen exchange, low flow (25mm/s)
- Nerve Fibre Layer
- Ganglion Cell Layer
- Inner Plexiform Layer
- Inner third of inner nuclear layer
What is the flow rate of the choroidal vessels? What layers do they supply?
Low oxygen exchange, high flow rate (150mm/s)
1. Outer 2/3rds of inner nuclear layer
2. Outer plexiform layer
3. Outer nuclear Layer
4. Photoreceptors
5. RPE
What is present in the photoreceptor layer of the retina?
Only OUTER SEGMENTS and INNER SEGMENTS (mitochondria) of rods and cones.
What is the outer/external limiting membrane?
Formed by Muller cells and serpates the inner and outer segments of the photoreceptors from their cell bodies.
This Bisects area of rods/cones at the level of the nucleus
What is present in the outer nuclear layer?
Nuclei of the rods and cones (photoreceptor cell bodies)
What is the outer plexiform layer? What is its main function?
Synapses / axons / dendrites between rods/cones and bipolar cells and horizontal cells
Watershed zone between outer third of neural retina (photoreceptor) supplied by choroid and inner 2/3rds supplied by the central retinal artery
Contains the deep capillary plexus, most common site for fluid accumulation in CMO.
Whatis contained within the inner nuclear layer?
Nuclei of the bipolar cells, horizontal cells, amacrine and muller cells
