Retina Flashcards
بسم الله الرحمن الرحيم
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Mention layers of Retina
Pigmented epithelium
Layer of phororeceptors
Outer limiting membrane
Outer nuclear Layer
Outer plexiform layer
Inner nuclear layer
inner plexiform layer
Ganglion cell layer
Optic nerve fibers
Inner limiting membrane
¶ Retina is transparent.
¶ Retina has no pain nerve supply → painless.
¶ The outer 5 layers of retina supplied from ???????
¶ The inner 5 layers of retina supplied from ???????
but there is no sufficient anastomosis between these vessels.
¶ Retina has no lymphatics.
Choroid blood vessels
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inner retinal + choroid blood vessels
Mention nucelar cells of retina
Outer nuclear for ( Rods and cones nuclei
Inner nuclear for ( Bipolar + horizontal + amacrine
Gagnlion cell layer
retinal detachment is damaging to the receptors. of rods and cones why?
Because Rods and cones receptors are supplied by Capillary pleux in the choroid
Bipolar and ganglion cells are supplied by?
Retinal blood vessels
A single melanin containing cell layer in a direct contact with
choroid.
Mention it and its functions
Pigmented epitehlium layer ASP
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-Absoprtion of extra light cannor bea absorbed by Rods and cones photoreceptors preventing Ligth reflection
-Storage of Lare quantities of Vit A
-Phagocytosis of membrene discs and debris of photoreceptors
Inner nuclear layer of Retina explain
Formed of Bipolar cells + Amacrine + Horizontal
Muller
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Bipolar receive imupulse from Photorecpetors or Horiztontal cells to sends it to Ganglion cells
1-directly
2-indirectly thorugh amacrine cells
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Bipolar cells are the First 1st order neuron
Mention types of Bipolar cells
Depolarizing due to stimulation by Photoreceptros Glutamate
Hyperpolarizing due to inhibtion by Horizontal cell GABA
Mention functions of Bipolar cells
1-First 1st order neruon of Visual pathway
2-Contrast due to Lateral inhibtion
Mention functions of Horizontal cells
Most imp cell of lateral inhibtion receving from Photoreceptors
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Lateral inhibtion of Weakley or non stimulated Pathways = Enhancement of Contrast +sharpening of borders
Lateral inhibtion of some color specific ganglion cells for color differentiation
Mention functions of amacrine cells
Carries impulses from bipolar to ganglion cells
Resonsible for Sharpening of Vision + Vision analysis
Onset of visual signals
Offset of Visual signals
Bilateral amacrine cells respnds to movement of a spot across retina in a specific direction
Mention functons of Muller cells >
Forming outer &inner limiting membranes
Retinal metabolism in
-storing Glycogen
-Removal of debris + uptake of NTs
The Ganglion cells:
????? order neurons in visual pathway
Receive impulses from?????& ?????cells.
Their axons form o????????
Continuously transmit impulses to the brain.
2nd order Neuron
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Bipolar + Amacrine
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Optic nerve fibers
Compare between Magnocellular and parvocellular Ganglion cells ( حجم مجال منتهي مسئولية”
Size:
Magno: Large rapid
Parvo : small slower
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Receptice field:
Magno Large less acuity
Parvo : small more acuity
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Projecto to ?
Magno to Magnoceulluar layer of LGB
Parvo to parcocellular layer of LGB
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Respnisible for :
Magno for Movement + Light intensity
Parvo for Boundaries + edges + Details
Particular area of retina sending impulses to certain Bipolar + Ganglion cells
Receptive field
Large in Magnocellular so less acuity so for movement and ligth inetensity
Less in parcocellular so high acuity so for Details + boundaries and edges
Optic disc ( physiological blind spot):
1.5 mm in diameter.
3 mm …….to the center of retina.
Why called blind spot ?
Pale pink, well defined, has a physiologic cup.
At which:
???
1-
2-
3-
Medial to center
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blind spot as it is insensitive to light and has no photoreceptors
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At which
All retinal layers end except ? Ganglion cell fibers
Retinal vessels enter
Optic nerve exit
Optic disc abnormailtis :-
a) ↑ cupping: by?????
b) Swelling (papilledema): by ??????
c) White disc with deep cupping: ????
a)Increased IOP
b)Increased Intracranial pressure
c) Optic atrophy
Macula lutea:
Yellowish spot at the center of retina.
Contains MAINLY???photoreceptor
Contains ?????, which is a special type of melanin that:
??????
1-
2-
3-
Cones
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Xanthopyll
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1-Absorb extra light
2-Xanthopyll works as antioxidant
3-Xanthopyll prtoects photorecptors by filtring UV rays
Area of sharpest vision ?
site?
photorecpetos?
Fovea centralis
Center of Macula lutea (center of center of vision)
Photorecpetors : = Cones only 1:1 to bipolar cells
GR/Fovea centralis is the sharpest vision area
Contains only cones!
Light falls directly on cones due to no BVs + layers of retina are displaced to sides
Each cone connected to one Bipolar to single Ganglion to single optic nerve fiber 1:1 with no convergence for more sharpness
Pigmented Xanthopyll epithelium
Donut vision explain
When there is age related mauclr degneration which is degeneration of photoreceptors in Macula +Fovea
this leads to :
Loss of central shapest vision
Perservation of less sharp Periopheral vision
causing Donut vision
Compare between Fovea and Extra Foval regions
in
1-Receptors
2-Connections
Receptors :
Fovea: Only small cones
ExtraF: Rods mainly + large cones
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Connections:
Fovea : 1:1:1 single cone to single bipolar to single ganglion cell
ExtraF: 200 -300 receptors : 1 bipolar
5 bipolar : 1 ganglion
Compare between fovea and extra foveal region in
Nutirition
Fovea: Avascular depends on choroid Capillary by diffusion
ExtraFovea: Choroid and Retinal BVs
Compare between Fovea + extra fovea in
Sensitivity
Threshold
Acuity
Colors
Vision
Sensitivtiy and threshold and acuity:
Fovea less sensitive with high threshold and high acuity of vision so diffentiate colors and used in Photopic vision =vision of the day
ExtraFovea :more sensitive with less thresholld and low acuity so cannot differentiate colors for Scotopic vision dim light of night +photopic also
