histological and physiological discription of the retina or tunica interna or tunica nervosa. an important structure in the eye to conduct the visual impulses from physical world to the brain.

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Retina..
By : Shlok Mathur

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Introduction…
The retina is a thin layer of tissue that lines the back of the eye
on the inside.
The purpose of the retina is to receive light that the lens has
focused, convert the light into neural signals, and send these
signals on to the brain for visual recognition.
The retina processes a picture from the focused light, and the
brain is left to decide what the picture is.

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Layers of Retina..
The 2 fundamental sublayers of
the Retina are :
 Outer Pigmented Layer -
simple cuboidal epithelium.
 Inner Neural Layer – stratified
with various neurons and
photoreceptors.

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Pigmented Epithelium..
The pigmented epithelial layer consists of
cuboidal or low columnar cells with basal nuclei
and surrounds the neural layer of the retina.
Function :
 Absorbs Scattered Light
 Blood Retina Barrier
 Retinal Regeneration
 Phagocytosis
 Removes Free Radicals and
Supports Neural Layer.

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Neural Retina..
The neural retina consists
of several layers of
neurons interconnected by
synapses, and is supported
by an outer layer of
pigmented epithelial cells.

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Layer of Rods
and Cones..
The rod and cone cells,
named for the shape of their
outer segments, are
polarized neurons with their
photosensitive portions
aligned in the retina’s rod
and cone layer (RCL) and
their axons in the OPL.

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Limiting Membranes..
External Limiting Membrane
External limiting membrane is a thin layer,
formed by the chief supporting elements
of retina called the Müller fibers.
Internal Limiting Membrane
Internal limiting membrane is the innermost
layer of retina and it separates retina from
the vitreous body.
It is a hyaline membrane, formed by the
opposition of expanded ends of Müller
fibers.

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Nuclear Layers…
Inner Nuclear Layer.
The inner nuclear layer contains
the nuclei of various neurons,
notably the bipolar cells, amacrine
cells, and horizontal cells.
Outer Nuclear Layer.
Near the pigmented epithelium,
the outer nuclear layer contains
cell bodies of photoreceptors (the
rod and cone cells).

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Plexiform Layers..
Outer Plexiform Layer..
The outer plexiform layer
includes axons of the
photoreceptors and dendrites of
association neurons in the INL.
Inner Plexiform Layer..
The inner plexiform layer
consists of axons and dendrites
connecting neurons of the INL
with the ganglion cells.

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Ganglionic Cell
Layer..
Multipolar cells are present
in this layer. Some cells are
large and are called giant
ganglion cells. Other cells
are smaller called midget
ganglion cells. Axons from
ganglion cells are in the
inner surface of the retina.

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Layer Of Nerve
Fiber..
Layer of nerve fibers is formed by
non-myelinated axons of
ganglionic cells. After taking origin,
the axons run horizontally to a
short distance. Afterwards, the
fibers converge towards the optic
disk and form the optic nerve.
Neuroglial cells, Müller cells and
retinal blood vessels are also
present in this layer.

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Fundus Oculi..
Fundus oculi is the posterior part of
interior eyeball. It is also called
fundus. In living subjects, fundus is
examined by ophthalmoscope.
Fundus has two important
structures:
1. Optic disk
2. Macula lutea with fovea
centralis.

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Thank you..
Doubt..??