Eye, retina

Note that the appearance of the retina varies with location.  The concentration of cells (and resulting thickness of the retina) decreases toward the periphery (i.e., with increasing distance from the macula).

Retinal layers

• The green line at the top of the image (above the nerve fiber layer) is the site of the inner limiting membrane, a basal lamina separating nervous tissue of the retina from connective tissue of the vitreous humor. 
• The layer of nerve fibers contains axons from ganglion cells which travel across the retina to the optic nerve and hence past the optic chiasm into the optic tract and into lateral geniculate nucleus of the thalamus.
• The ganglion cell layer contains the cell bodies of ganglion cells, the cells whose axons project to the brain.
• The inner plexiform layer contains dendrites of ganglion cells synapsing with axons of bipolar cells.
• The inner nuclear layer contains the cell bodies of bipolar cells
• The outer plexiform layer contains dendrites of bipolar cells synapsing with axons of photoreceptor cells.
• The outer nuclear layer contains the cell bodies of receptor cells.
• The receptor layer contains the photoreceptive outer segments (rods and cones) of receptor cells.
• The pigmented epithelium absorbs light not captured by photoreceptors, and also contributes to the maintenance of rods and cone outer segments.
• The red line between the outer nuclear layer and the receptor layer is the site of the outer limiting membrane, a basal lamina bounding the neural retina.  The outer segments (rods and cones) of the receptor cells penetrate the outer membrane to contact the pigmented epithelium.

Formation of neural retina and pigmented epithelium

The retina forms from the optic vesicle, which evaginates from the neuroectodermal diencephalic vesicle.  The optic vesicle remains attached to developing brain; the connection between optic and diencephalic vesicles becomes the optic nerve. 

The optic vesicle itself collapses into a cup.  The front surface of this vesicle (the hollow of the cup) becomes the neural retina, while the back surface becomes the retina's pigmented epithelium. 

Although cells of the pigmented epithelium are intimately associated with outer segments (rods and cones) of receptor cells, this surface where the neural retina contacts the pigmented epithelium is inherently extremely fragile and is the site where retinal detachment can occur.

 

Comments and questions: dgking@siu.edu

SIUC / School of Medicine / Anatomy / David King

http://www.siumed.edu/~dking2/ssb/EE020b.htm
Last updated:  30 November 2004 / dgk