Anatomical orientation:
The vitreous chamber lies internal to the retina.
The choroid lies external to the retina.
the ten layers.
1. The pigmented layer
- Retinal retinal pigmented epithelium (commonly abbreviated RPE).
It is involved in photoreceptor metabolism and that it comprises which captures light not picked up by the photoreceptors.
2. The photoreceptor cell layer of rods and cones
It is involved in light capture and PHOTOTRANSDUCTION; the phototransduction cascade occurs here, which transforms light into neural signal. The photoreceptor cell segments are metabolically dependent upon the pigmented epithelium for photoreceptor regeneration and waste disposal.
This layer divides into:
- An outer segment
- An inner segment.
3. External limiting membrane
4. Outer nuclear layer
- Photoreceptor cell bodies.
Cones have a large outer, conical segment; they provide high-resolution color vision.
Rods have a small, narrow cylindrical outer segment; they provide low-resolution dim-light ("night") vision.
We draw more rods than cones, here, to reflect that rods outnumber cones by roughly 15:1.
Cones predominate in central vision (within the fovea), whereas rods predominate in peripheral vision (outside of the macula).
5. Outer plexiform layer
It comprises a thin synaptic zone; we'll draw these synapses momentarily.
6. Inner nuclear layer
It comprises retinal interneuronal cell bodies.
- This layer specifically comprises:
BIPOLAR CELLS, which, as we see have two poles, so they can pass forward electrical signal from the photoreceptor cells to the ganglion cells (drawn soon).
HORIZONTAL and AMACRINE CELLS, which enhance visual contrast.
It is well recognized that the visual system relies more on visual contrast than the overall level of illumination for visual perception. The visual system attends to the borders between light and dark areas or color differences more so than light intensity. As long as we can read the page of a book comfortably, we perceive the words on it just the same in varying levels of illumination; it is the contrast of the ink from the page that makes the largest impression in our mind.
MÜLLER GLIAL CELLS extend across the retina: their proximal endings form the inner limiting membrane (as we'll soon see) and their distal processes help form the external limiting membrane.
7. Inner plexiform layer
It comprises a thick synaptic zone.
8. Ganglion cell layer
It comprises ganglion cell bodies.
The ganglion cell dendrites help form the inner plexiform layer, and the axons form the nerve fiber layer.
9. Nerve fiber layer
It comprises axons of the ganglion cells, which are unmyelinated.
10. Inner limiting membrane
It forms from the basal lamina of Müller glial cells.
