Applied anatomy and physiology of the orbit and eye Flashcards
What type of epithelium lines the cornea?
Stratified squamous, non-keratinized
Lines both sides (endothelium inner layer)
What is the basement membrane of the cornea epithelium called?
Bowman’s Membrane
What is the corneal stroma?
The regularly arranged collagen of the cornea,
Does not contain blood vessels - to keep it transparent
What is Descemet’s layer?
The endothelium of the cornea (inner)
What mechanism of the endothelium of the cornea (Descemet’s layer) helps maintain transparency of the cornea?
If there is damage to this layer what can happen?
The endothelium has a pump to actively keep the Aqueous Humor out
Decreasing the endothelial cell count reduces ability to keep AH out, it then enters the cornea and makes the cornea more cloudy/less transparent
Why is a corneal transplant easier than many other transplants in different systems? (eg. liver/renal)
Because the cornea is avascular and so there is less of a chance that foreign antigens from a donor will be rejected
Describe the blood supply to the retina
- The outer layers are supplied by the choroid
- The inner layers are supplied by the central retinal artery
3 Layers of retina you should know? (/10)
Layer 1 - pigment epithelial layer
Layer 2 - Layer of rods and cones
Layer 9 - Nerve fibre layer (axons that join to form the optic nerve)
How many layers of nerve fibres make up the retina?
3 layers
- 2 synapses
Main function of the pigment epithelial layer of the retina?
What happens when it degenerates?
It is important in maintaining the health of the retina
Age related macular degeneration - degeneration of this layer in old age causes reduced ability to see
Why is the layering of the retina inefficient?
Where is this not the case?
Because the rods and cones are deep to 8 layers of retina, light has to travel through them before the image is formed
Not the case at the fovea centralis
Where is the point of best visual acuity? Why is this the case?
At the Fovea centralis
Here there are more cones, and the overlying layers of the retina are off to the side of the cones, leaving them closer to the surface - less layers to penetrate + more cones
Why do you move your eyes to focus on your periphery despite being able to sort of see there in the first place?
Because vision in the peripheries is not as good as at the fovea centralis, if you move your eyes so that the image focuses on the fovea you get much more visual acuity
Necessary for things like reading
Why is the lens predisposed to become opaque?
Because it is avascular
And UV ray absorption can damage the fibres of the lens
