Layers Of The Retina

Ten layers of cells and their processes constitute the neural retina

Before discussing the ten layers of the retina, it is important to identify the types of cells found there. This identification will aid in understanding the functional relationships of the cells. Studies of the retina in primates have identified at least 15 types of neurons that form at least 38 different types of synapses. For convenience, neurons and supporting cells can be classified into four groups of cells (Fig. 23.9):

• Photoreceptors—the retinal rods and cones

• Conducting neurons—bipolar and ganglion cells

• Association and other neurons—horizontal, centrifugal, and amacrine

• Supporting cells—Miiller's cells and neuroglial cells

The specific arrangement and associations of the nuclei and processes of these cells result in the retina being organized in ten layers that are seen with the light microscope. The ten layers of the retina, from outside inward, are (Figs. 23.9 and 23.10)

1. Pigment epithelium—the outer layer of the retina, actually not part of the neural retina but intimately associated with it

2. Layer of rods and cones—contains the outer and inner segments of photoreceptor cells

3. Outer limiting membrane—the apical boundary of Miiller's cells

4. Outer nuclear layer—contains the cell bodies (nuclei) of retinal rods and cones incident light inner limiting membrane cells optic nerve fiber layer inner plexiform layer outer plexiform limiting membrane

Müller's cells amacrine bipolar cells horizontal cells inner segment of cone and rod outer segment of cone and rod

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