An entire retina contains about 6 million cones – about one-twentieth the number of rods. However, cones are the only type of light-sensitive cell found in the primate fovea, where they are massively concentrated.
The cone-shaped outer segment of a cone cell, which is the light-sensitive part, consists largely of a stack of parallel unit membranes at right angles to the cell length. It develops embryologically from a cilium and retains its characteristic 9+2 pattern of fibrils.
Related categories• ANATOMY AND PHYSIOLOGY
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