External Limiting Membrane separates which parts?

External Limiting Membrane separates which parts?

• A. Outer segments from inner segments
• B. Photoreceptors from bipolar cells
• C. Inner segments from cell nuclei
• D. Retinal layers from vitreous

Answer: (C)

The External Limiting Membrane is a thin barrier formed by tight junctions between photoreceptor inner segments and the end of Müller glial processes, sitting at the outer edge of the photoreceptor layer. This arrangement places the photoreceptor nuclei in the outer nuclear layer below and the inner segments above, so the ELM separates the inner segments from the cell bodies (nuclei). It’s not the boundary between outer and inner segments (that interface is within the photoreceptor itself), nor the boundary between photoreceptors and bipolar cells (that region is the outer plexiform layer), nor the boundary with the vitreous (that’s the internal limiting membrane).

The External Limiting Membrane is a thin barrier formed by tight junctions between photoreceptor inner segments and the end of Müller glial processes, sitting at the outer edge of the photoreceptor layer. This arrangement places the photoreceptor nuclei in the outer nuclear layer below and the inner segments above, so the ELM separates the inner segments from the cell bodies (nuclei). It’s not the boundary between outer and inner segments (that interface is within the photoreceptor itself), nor the boundary between photoreceptors and bipolar cells (that region is the outer plexiform layer), nor the boundary with the vitreous (that’s the internal limiting membrane).