Which layer of the retina contains the cell bodies of the bipolar, horizontal, amacrine, interplexiform, and Muller cells?

• A. Ganglion Cell Layer
• B. Inner Nuclear Layer
• C. Outer Nuclear Layer
• D. Inner Plexiform Layer

Answer: (B)

The inner nuclear layer houses the cell bodies of several retinal interneurons and glia, including bipolar, horizontal, amacrine, interplexiform, and Müller cells. Bipolar cells relay signals from photoreceptors to ganglion cells, and their somas live in this layer. Horizontal and amacrine cells, which provide lateral and inhibitory processing, also have their cell bodies here, as do interplexiform cells whose bodies reside in this layer and send processes to both plexiform layers. Müller cells, the main retinal glia, have their cell bodies in the inner nuclear layer and extend their processes throughout the retina to support and insulate neural elements. In contrast, the outer nuclear layer contains photoreceptor cell bodies, the ganglion cell layer contains ganglion cell bodies, and the inner plexiform layer is where synapses occur, not where these cell bodies reside.