Which sequence correctly lists retinal layers from outermost to innermost?

Which sequence correctly lists retinal layers from outermost to innermost?

• A. Photoreceptors (outer segments) -> Outer Nuclear Layer -> Outer Plexiform Layer -> Inner Nuclear Layer -> Inner Plexiform Layer -> Ganglion Cell Layer
• B. Photoreceptors -> Inner Plexiform Layer -> Outer Nuclear Layer -> Outer Plexiform Layer -> Inner Nuclear Layer -> Ganglion Cell Layer
• C. Photoreceptors (outer segments) -> Outer Plexiform Layer -> Outer Nuclear Layer -> Inner Nuclear Layer -> Inner Plexiform Layer -> Ganglion Cell Layer
• D. Photoreceptors (outer segments) -> Inner Nuclear Layer -> Outer Plexiform Layer -> Outer Nuclear Layer -> Inner Plexiform Layer -> Ganglion Cell Layer

Answer: (C)

The sequence tests how the retina is layered along the axis from the outside (toward the choroid) to the inside (toward the vitreous) and where the key cellular and synaptic sites lie. Photoreceptors are the first to detect light, and their outer segments are adjacent to the retinal pigment epithelium. The cell bodies of these photoreceptors sit in the outer nuclear layer. The first synapses that relay signals from photoreceptors occur in the outer plexiform layer, where photoreceptor terminals connect to bipolar and horizontal cells. The next layer, the inner nuclear layer, contains the cell bodies of bipolar, horizontal, and amacrine cells. Then the inner plexiform layer houses the synapses between bipolar/amacrine cells and ganglion cells. Finally, the ganglion cell layer contains the cell bodies of the ganglion cells, whose axons form the optic nerve. So the correct order from outermost to innermost is: Photoreceptors (outer segments) → Outer Nuclear Layer → Outer Plexiform Layer → Inner Nuclear Layer → Inner Plexiform Layer → Ganglion Cell Layer. This arrangement reflects both the location of photoreceptor cell bodies and the progression of synaptic connections through the retinal circuitry.

The sequence tests how the retina is layered along the axis from the outside (toward the choroid) to the inside (toward the vitreous) and where the key cellular and synaptic sites lie.

Photoreceptors are the first to detect light, and their outer segments are adjacent to the retinal pigment epithelium. The cell bodies of these photoreceptors sit in the outer nuclear layer. The first synapses that relay signals from photoreceptors occur in the outer plexiform layer, where photoreceptor terminals connect to bipolar and horizontal cells. The next layer, the inner nuclear layer, contains the cell bodies of bipolar, horizontal, and amacrine cells. Then the inner plexiform layer houses the synapses between bipolar/amacrine cells and ganglion cells. Finally, the ganglion cell layer contains the cell bodies of the ganglion cells, whose axons form the optic nerve.

So the correct order from outermost to innermost is: Photoreceptors (outer segments) → Outer Nuclear Layer → Outer Plexiform Layer → Inner Nuclear Layer → Inner Plexiform Layer → Ganglion Cell Layer. This arrangement reflects both the location of photoreceptor cell bodies and the progression of synaptic connections through the retinal circuitry.