The Cellular Structure of the Retina

The Cellular Structure of the Retina

Retinas' cell populations and their development.

Top, A magnification of the retina in the human eye. The retina is composed of distinct layers: Inner limiting membrane: a basement membrane enriched with Muller glia cells; Nerve fiber layer: houses axons of the ganglion cells, which give rise to the optic nerve; Ganglion cell layer (GCL): contains nuclei of ganglion and displaced amacrine cells; Inner plexiform layer (IPL): the site of the synapses between the bipolar cell axons and the dendrites of the ganglion and amacrine cells; Inner nuclear layer (INL): contains the nuclei and cell bodies of the bipolar, horizontal, and amacrine cells, as well as Muller glia; Outer plexiform layer (OPL): contains the projections of rods, which end as rod spherules, and cones, which end as cone pedicles, both of which synapse with dendrites of bipolar and horizontal cells; Outer nuclear layer (ONL): houses the rod and cone cell bodies; Photoreceptor layer: a layer that contains the inner and outer segments of the rods/cones; The outer segments of photoreceptor cells associate with the retinal pigmented epithelium (RPE).

Bottom, The chronological order of generation of mammalian retinal cell types. Retinal ganglion and horizontal cells are generated first, followed, in overlapping phases, by cone-photoreceptors, amacrine cells, rod-photoreceptors, bipolar cells and, finally, Muller glia cells. The numbers relate to embryonic and postnatal days of murine development. 

Abbreviations: GCL, Ganglion Cell Layer; IPL, Inner Plexiform Layer; INL, Inner Nuclear Layer; OPL, Outer Plexiform Layer; ONL, Outer Nuclear Layer; RPE, Retinal Pigmented Epithelium.