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Abstract

This chapter presents the laminar organization of the vertebrate retina. It describes the inverted or correctly laminated retinotypic cellular spheres that can be raised by reaggregation from dissociated retinal cells of defined origin. These spheres are referred as “rosetted retinospheroids” or “stratospheroids.” Retinogenesis is resolved into distinct processes by comparatively analyzing the formation of retinospheroids. The optic system is considered a favorite model system for studying aspects of neural development or function as it represents an evolutionary, old, and very conservative part of the brain. Its embryonic development and adult state hardly differ in the different vertebrate groups. The basic buildup of retina from all different groups of vertebrates is very similar. The perikarya of rods and cones comprising the photoreceptor-cell population make up most of the scleral outer nuclear layer (ONL). Their synaptic terminals make characteristic ribbon synapses with horizontal and bipolar cells in the outer plexiform layer (OPL). The major glial elements of the retina are the radially running Muller cells. Depending on the species, additional glial elements such as microglia or astrocytes are present to varying degrees.