The Pigmentary Layer (also
known as the "Tapetum Nigrum") is the
tenth (10th)
of
the layers forming
the retina of
the human eye that light reaches after entering the eye: That is,
after light from outside the body enters the eye through it's main structures
of the cornea, aqueous
humour, pupil, lens,
etc..
The retina is composed of several layers which, together, form
the "screen" in the eye onto which an image of the area
viewed by the eye is formed, and information about that image is
segmented into packets of information that are passed to the
visual cortex of the brain via the optic
nerve.
The pigmentary layer (or "Tapetum
Nigrum") is
the most external - i.e. the most distant from the centre of the
eye, layer of the retina. It consists of a single layer of hexagonal
epithelial cells that contain pigment granules. The posterior (external)
surface of these epithelial cells is smooth, and in contact with
the choroid
layer.
The internal surfaces of these pigmented cells takes the form of straight
processes extending inwards between the rods - as shown in the pigment
layer at the top right-hand side of the top-right image on
this page.
Note that the pigmentary cells are also present in albinos, the
key difference being that in their cases the pigment granules are
not present.
For more information about related subjects see:
*_ Structure
& Components of the Eye,
*_ Components
of the Central Nervous System,
*_ The
Pathway of a Nerve Impulse,
*_ Structures
and Functions of Neurones,
*_ Diseases
and Disorders of the Nervous System,
*_ Text
books about Ophthalmology. |
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