Cornea
•Anterior 1/6th of tunica externa of wall of the eyeball.
•Cornea is transparent, avascular and richly innervated.
•Five layers of cornea are:
1. Anterior epithelium--outermost layer, non-keratinized
stratified squamous epithelium 4-5 layers thick.
2. Bowman's membrane (anterior limiting membrane) is
the thickened basement membrane of anterior epithelium.
3. Substantia propria-thickest layer consists of several
layers of collagen fibers with fibroblasts.
4. Descemet's membrane (posterior limiting membrane)
is the basement membrane of posterior epithelium.
5. Posterior epithelium-inner layer, simple squamous
endothelium.
• Regular arrangement of collagen fibers in substantia
propria and avascularity makes comea transparent.
• Rich nerve supply.
• Nutrition of cornea: Outer layers from-lear film,
inner layers-aqueous humor.
Retina
•Ten-layered structure.
• Outer most pigment cell layer, nuclear and ganglion
cell layer are prominent.
•Ten layers of retina are:
1. Pigment cell layer-outer most layer, cuboidal
cells with melanin pigments.Helps in absorption
of light, prevent reflection.
2. Rod and cones-contains outer segments of
photoreceptors (rods and cones).
3. External limiting membrane--formed by the
processes of Muller's cells.
4. Outer nuclear layer-contains cell bodies of
rods and cones. Rods associated with dim
and black and white vision, cones with bright
and color vision.
5. Outer plexiform layer-synapses between rods
and cones with peripheral processes of
bipolar cells,
6. Inner nuclear layer-cell bodies of bipolar cells,
amarine cells, horizontal cells.
7. Inner plexiform layer-synapses between central
processes of bipolar with peripheral processes
of ganglion cells.
8. Ganglion cell layer-large cell bodies of
ganglion cells.
9. Nerve fiber layer-axons of ganglion cells which
continue as optic nerve.
10. Inner limiting membrane--formed by the
processes of Muller's cells.
•Inner nine layers form neural layers of retina.
Rods and cones-photoreceptors.
Bipolar cells-first order neurons.
Ganglion cells-second order neurons.
•Nutrition of retina:
Inner layers from central artery of retina.
Outer layers-diffusion from capillaries plexus of choroid.