 Bipolar cells and their processes extend to both the inner and outer plexiform layer. In the peripheral regions of the retina, the axons of bipolar cells pass to the inner plexiform layer where they synapse with several ganglion cells. Through these connections, the bipolar cells establish communication with multiple cells in each layer except in the fovea, where they may synapse only with a single ganglion cell to provide greater visual acuity in this region.
 Horizontal cells and their processes extend to the outer plexiform layer where they intermingle with processes of bipolar cells. The cells have synaptic connections with rod spherules, cone pedicles, and bipolar cells. This electrical coupling of cells is thought to affect the functional threshold between rods and cones and bipolar cells.
 Amacrine cells processes pass inward, contributing to a complex interconnection of cells. Their processes branch extensively to provide sites of synaptic connections with axonal endings of bipolar cells and dendrites of ganglion cells. Besides bipolar and ganglion cells, the amacrine cells synapse in the inner plexiform layer with interplexiform and other amacrine cells (see Fig. 24.9).
 Interplexiform cells and their processes have synapses in both inner and outer plexiform layers. These cells convey impulses from the inner plexiform to the outer plexiform layer.
The inner plexiform layer (7) consists of a complex array of intermingled neuronal cell processes.
The inner plexiform layer consists of synaptic connections between axons of the bipolar neurons and dendrites of ganglion cells. It also contains synapses between intermingling processes of amacrine cells and bipolar neurons, ganglion cells, and interplexiform neurons. The course of these processes is parallel to the inner limiting membrane, thus giving the appearance of horizontal striations to this layer (see Fig. 24.10).
The ganglion cell layer (8) consists of the cell bodies of large multipolar neurons.
The cell bodies of large multipolar nerve cells, measuring as much as 30 m in diameter, constitute the ganglion cell layer. These nerve cells have lightly staining round nuclei with prominent nucleoli and Nissl bodies in their cytoplasm. An axonal process emerges from the rounded cell body, passes into the nerve fiber layer, and then goes into the optic nerve. The dendrites extend from the opposite end of the cell to ramify in the inner plexiform layer. In the peripheral regions of the retina, a single ganglion cell may synapse with a hundred bipolar cells. In marked contrast, in the macular region surrounding the fovea, the bipolar cells are smaller (some authors refer to them as “midget” bipolar cells), and they tend to make one-to-one connections with ganglion cells. Over most of the retina, the ganglion cells are only a single layer of cells. At the macula, however, they are piled as many as eight deep, although they are absent over the fovea itself. Scattered among the ganglion cells are small neuroglial cells with densely staining nuclei (see Fig. 24.10).
The layer of optic nerve fibers (9) contains axons of the ganglion cells.
The axonal processes of the ganglion cells form a flattened layer running parallel to the retinal surface. This layer increases in depth as the axons converge at the optic disc (Fig. 24.14). The axons are thin, nonmyelinated processes measuring as much as 5 m in diameter (see Fig. 24.10). The retinal vessels, including the superficial capillary network, are primarily located in this layer.
The inner limiting membrane (layer 10) consists of a basal lamina separating the retina from the vitreous body.
The inner limiting membrane forms the innermost boundary of the retina. It serves as the basal lamina of Mler’s cells (see Fig. 24.10). In younger individuals, refections from the internal limiting membrane produce a retinal sheen that is seen during ophthalmoscopic examination of the eye.
Specialized Regions of the Retina