Macroglia are cells that regulate the retinal metabolism and modulate neuron function and blood vessels. There are two cell types as part of the macroglia: Miiller cells and astrocytes. The Muller cells cross the thickness of the retina from the RPE to the inner limiting membrane. The bodies of the cells are located in the inner nuclear layer, and they are the principal regulatory cells for the metabolism of glutamate, the ion balance, and neuron function. The Muller fibers form an extended net that sustains and surrounds all the nervous cells. In addition, their axons and dendrites help to form the inner and outer limiting membranes.
The astrocytes, on the contrary, are limited to the nervous fiber layer and envelope the blood vessels and ganglion cells with their cellular protrusions. The branched protrusions of these cells occur at right angles with respect to the Muller fibers, and the two structures are not linked. The astrocytes are star-shaped, with round nuclei and numerous thin protrusions. They are horizontally placed and surround the blood vessels with a dense net of fibers. They form an arched, honeycomb structure, which surrounds and sustains the axons of the ganglion cells. They are firmly anchored to the walls of the blood vessels (Vernadakis, 1986).
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