Anatomy microsopic structure

1. ANATOMY OF RETINA
By
G.Jagadeesh
Roll no : 43

2. INTRODUCTION
• It’s the internal layer of eyeball.
• A thin transparent membrane having a purplish-red color.
• Thickness>> 0.56mm near the optic disc to 0.1mm at the ora serrata…
while it’s thinnest at the fovea centralis.
• Continuous posteriorly with the optic nerve, while anteriorly
with the ciliary body & iris epithelium.
• Bordered by the vitreous internally & the Bruch’s membrane
externally.
• Firmly attached at the margins of optic disc and at its anterior
termination at the ora serrata .
• Approximate landmark on outside of the eye; medially insertion of
medial rectus, laterally insertion of lateral rectus (closer to the
limbus nasally)

4. • It consists of an :
-outer retinal pigment epithelium. (RPE) (derived
from outer layer of optic cup).
-inner neurosensory layer.
(derived from inner layer of optic cup).
• Macula lutea: an oval ,yellowish area ,at the center of the
posterior part of retina… It has central depression called the
fovea centralis.
• The optic disc: a 3-mm depression of the retina where the optic
nerve leaves… pierced by the central retinal artery & vein… Blind
spot.

6. EMBRYOLOGY
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The outer layer of the optic cup is known as the
pigmented layer of the retina.
Development of the inner (neural) layer of the optic cup is
more complicated.
The posterior four-fifths, the pars optica retinae, contains
cells bordering the intraretinal space that differentiate into
light-receptive elements, rods and cones.
Adjacent to this photoreceptive layer is the mantle
layer, which, as in the brain, gives rise to neurons and
supporting cells, including the outer nuclear layer, inner
nuclear layer, and ganglion cell layer.

8. MICROSCOPIC STRUCTURE OF RETINA
It has 10 layers:
1. Retinal pigment epithelium
2. Layer of rods and cones
3. External limiting membrane
4. Outer nuclear layer
5. Outer molecular (plexiform) layer
6. Inner nuclear layer
7. Inner molecular (plexiform) layer
8. Ganglion cell layer
9. Nerve fibre layer
10. Internal limiting membrane

11. RETINAL PIGMENT EPITHELIUM
• Hexagonally arranged single layer of narrow & tall cells from the
margin of the optic nerve flattening gradually towards the ora
serrata.
• The basal end of each cell is infolded and rests on a
B.M which forms a part of the Bruch's membrane.
• Apically shows microvili (5-7um long ), which project
between & adhesively bind with rods & cones but with no
specialized attachments.
• The adjacent cell membrane are bound together in basal region by
zonula adherens, and in apical region by zonula occludens.

13. NEURAL RETINA
Photo receptors
*Rods:
- 110-125 milion .
- denser at the periphery (absent at fovea)
- responsible for vision in dim light
producing images of varying shades of
black & white.
*Cones:
-number about 6.3-6.8milion .
-highest density at the fovea
-responsible for color vision in bright light.

16. BIPOLAR CELLS
• First order neuron in visual pathway.
• one or more dendrites pass outward to synapse
with photoreceptor cell terminal .
• The single axon is directed inward to synape with
ganglion cell and amacrine cells.
• Types:
-Rod bipolar cells: connecting rods to ganglion cells,
-Flat or diffuse bipolar cell: connect cones to
ganglion cells,
-Midget bipolar cell: connect a single cone cell to a
single midget ganglion cell.

17. GANGLION CELLS
• Second order neuron in visual pathway.
• Only 100 million ganglion cells in the retina; meaning
more than 100 photoreceptors per ganglion cell.
• Single layer in periphery and increase towards the
macula while completely absent at the fovea.
• Nonmyelinated intraocular & become myelinated just
after leaving the lamina cribrosa.
• The myelin sheath is formed by oligodendrocytes.
• If intraocular part gets myelinated, it results in a blind
spot.

19. BLOOD SUPPLY
• Dual supply:
• The outer laminae (down to the outer nuclear) by the
choroidal capillaries
• The inner laminae by the cental retinal artery & vein
• The integrity of the retina depends on both of these
circulations, neither of which alone is sufficient & there’s No
anastomosis.