The inner nuclear layer or layer of inner granules, of the
retina
The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...
, is made up of a number of closely packed cells, of which there are three varieties, viz.: bipolar cells, horizontal cells, and amacrine cells.
Bipolar cells
The
bipolar cell
A bipolar neuron, or bipolar cell, is a type of neuron that has two extensions (one axon and one dendrite). Many bipolar cells are specialized sensory neurons for the transmission of sense. As such, they are part of the sensory pathways for sme ...
s, by far the most numerous, are round or oval in shape, and each is prolonged into an inner and an outer process.
They are divisible into rod bipolars and cone bipolars.
* The inner processes of the
rod bipolars run through the
inner plexiform layer
The inner plexiform layer is an area of the retina that is made up of a dense reticulum of fibrils formed by interlaced dendrites of retinal ganglion cells
A retinal ganglion cell (RGC) is a type of neuron located near the inner surface (the g ...
and arborize around the bodies of the cells of the
ganglionic layer; their outer processes end in the outer plexiform layer in tufts of fibrils around the button-like ends of the inner processes of the rod granules.
* The inner processes of the
cone bipolars ramify in the inner plexiform layer in contact with the dendrites of the ganglionic cells.
Connection types
Midget bipolars are linked to one cone while diffuse bipolars take groups of receptors. Diffuse bipolars can take signals from up to 50 rods or can be a flat cone form and take signals from seven cones. The bipolar cells corresponds to the intermediary cells between the touch and heat receptors on the skin and the medulla or spinal cord.
["eye, human."Encyclopædia Britannica. 2008. ]Encyclopædia Britannica 2006 Ultimate Reference Suite DVD
An encyclopedia (American English) or encyclopædia (British English) is a reference work or compendium providing summaries of knowledge either general or special to a particular field or discipline. Encyclopedias are divided into articles ...
Horizontal cells
The
horizontal cells lie in the outer part of the inner nuclear layer and possess somewhat flattened cell bodies.
Their dendrites divide into numerous branches in the outer plexiform layer, while their axons run horizontally for some distance and finally ramify in the same layer.
Amacrine cells
The
amacrine cell
Amacrine cells are interneurons in the retina. They are named from the Greek roots ''a–'' ("non"), ''makr–'' ("long") and ''in–'' ("fiber"), because of their short neuronal processes. Amacrine cells are inhibitory neurons, and they projec ...
s are placed in the inner part of the inner nuclear layer, and are so named because they have not yet been shown to possess axis-cylinder processes.
Their dendrites undergo extensive ramification in the inner plexiform layer.
References
External links
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Human eye anatomy