RETINA

Question 1

Layers of the retina.

Answer 1

1. RPE- retinal pigmented epithelium
2. Photoreceptor layer.
3. External limiting membrane.
4. Outer nuclear layer.
5. Outer plexiform layer.
6. Inner nuclear layer.
7. Inner plexiform layer.
8. Ganglion cell layer.
9. Optic nerve fiber layer.
10. Internal limiting layer.

Question 2

RPE

Answer 2

Retinal pigmented epithelium. The outermost retinal layer- creating the non-sensory retina. Lays between choroid and photoreceptor layer and contain melanin granules. It’s dark brown except for the part with tapetum. The main role of that layer is to provide nutrition for the neurosensory retina, recycling of the bleached ‘used’ photopigment, storage of the vitamin A, phagocytosis, absorb stray light and free radicals.

Question 3

Photoreceptor layer.

Answer 3

Outer segments of rods and cones that contain stacked discs with photopigment, and part of the inner segments with mitochondria. Here’s where transduction of light stimulus happens.

Question 4

Outer nuclear layer.

Answer 4

Cell bodies of rods and cones.

Question 5

Outer plexiform layer.

Answer 5

Synaptic connections between photoreceptors and bipolar, amacrine and horizontal cells.

Question 6

Inner nuclear layer.

Answer 6

Cell bodies of horizontal, bipolar, amacrine and Mullers cells.

Question 7

Inner plexiform layer.

Answer 7

Is the second synaptic layer between axons of amacrine, bipolar, horizontal cells and retinal ganglion cells.

Question 8

Ganglion cell layer.

Answer 8

cell bodies of the RGCs, usually one cell thick, axons of these cells run parallel to the retina and converge onto the optic disc.

Question 9

Nerve fibre layer.

Answer 9

Axons of the RGCs that run parallel to the retina and converge onto the optic disc.

Question 10

Internal limiting layer

Answer 10

Basement layer, the border between the retina and vitreous.

Question 11

Types of cells that form neuro-retina.

Answer 11

Rods, cones, amacrine, horizontal, bipolar, interplexiform neurons, Muller’s cells, retinal ganglion cells.

Question 12

Blood supply to the retina.

Answer 12

Dual blood supply (as the most metabolically active tissue in the body). 1- Choroid vessels that supply outer retina and 2- retinal vessels that supply mid and inner retina 2- in most mammals, they’re branches of posterior ciliary arteries called cilioretinal arteries and penetrate the sclera in a circle around the optic disc.

Question 13

Patterns of retinal vasculature.

Answer 13

Holangiotic- whole retina is transversed with vessels.
Merangiotic- laterally and medially extending vessels.
Paurangiotic- short vessels, radiating around the optic disc.
Anangiotic- no vessels.

Question 14

Holangiotic retina- pattern and which animals.

Answer 14

The whole inner retina receives a direct blood supply, either from a central artery (primates) or from cilioretinal arteries that emerge as several branches from or around the optic disc.
Most mammals (including dog, cat, sheep, cow, rat, mouse, primates and some marsupials)

Question 15

Merangiotic retina- pattern and which animals.

Answer 15

Blood supply localized to the nasal and temporal parts of the inner retina.
Rabbit, pika.

Question 16

Paurangiotic ratina- pattern and which animals.

Answer 16

The vessels are minute and extend only a short distance from the optic disc, leaving most of the inner retina avascular.
Horse, rhinoceros, elephant, guinea pig

Question 17

Anangiotic retina- pattern and which animals.

Answer 17

Devoid of vessels.
Most non-mammalian species: birds, reptiles, amphibians.
From mammals- most marsupials, beaver, chinchilla, porcupine, armadillo, sloth, bats.

Question 18

What is characteristic in avian retina.

Answer 18

The presence of pecten- structure that protrudes into the vitreous from the retina.

Question 19

What is characteristic in reptilian and amphibian retina.

Answer 19

The presence of conus papillaris arising from the optic disc.