Basic Structure and Orientation of the eye (tuesday week 2) Flashcards
Understand the Basic Structure and Orientation of the eye…
Need to know and how to label…
- sclera
- choroid
- retina
- lens
- pupil
- cornea
-RPE
-Cone
-Rod
- Horizontal cell
- bipolar cell
- muller glia
- amacrine cell
- ganglion cell
- optic nerve
- blind spot
- photoreceptor cell
- ciliary muscle
- lens
- iris
- nerve fibers
- optic ganglion?
DORSAL VS VENTRAL SIDE
The octopus retina is “upside down”… What is the advantage?
- inverted retina actually is a superior space-saving solution, especially in small eyes.
The inverted retina has most likely facilitated the evolution of image-forming eyes in vertebrates, and it still benefits especially small and highly visual species.
Compare Octopus retina and human retina (cross sections, histology)
Comapre human vs octopus eye balls
draw and label both
slide 4 and slide 5
What retinal ganglion cells are and what they do
Retinal ganglion cells (RGCs) are the bridging neurons that connect the retinal input to the visual processing centres within the central nervous system.
Retinal ganglion cells (RGC) bear the sole responsibility of propagating visual stimuli to the brain
Ganglion cells are the projection neurons of the vertebrate retina, conveying information from other retinal neurons to the rest of the brain.
*What photoreceptors are and what they do?
Special cells in the eye’s retina that are responsible for converting light into signals that are sent to the brain.
Photoreceptors give us our colour vision and night vision.
Photoreceptor cell -
A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction.
The great biological importance of photoreceptors is that they convert light (visible electromagnetic radiation) into signals that can stimulate biological processes.
There are two types of photoreceptor cells: rods and cones.
The cones are responsible for daytime vision, while the rods respond under dark conditions.
The cones come in three varieties: L, M, and S types (for long, middle, and short wavelength).
what is INNER NUCLEAR LAYER in eye?
Inner nuclear layer:
filters out “random noise”
- found between ganglion cells and photoreceptors
Draw ganglion cells, inner nuclear layer and photoreceptors…
slide 6
Which species can read fine print?
Which species can see in the dark?
Human vs octopus
- Human
- octopus
Which species has high acuity?
which species has high sensitivity?
slide
- species 3: one to one ratio of photoreceptor has partner ganglion cell
- species 4 - MASSES of photoreceptors, less ganglion cells - more likely to capture
What does Retinal vasculature looks like in different species…
BLOOD SUPPLY DEVELOPMENT AMPHIBIA
BLOOD SUPPLY DEVELOPMENT AMPHIBIA : - ‘Hyaloid (vitreal) vessels stay’
- ONLY ON FRONT SURFACE (“net stocking”)
- eg frogs
BLOOD SUPPLY DEVELOPMENT AMPHIBIA : - ‘Hyaloid (vitreal) vessels stay’
look at frog vs tadpole VENTRAL ENTRYB POINT AND DIAGRAM
- Ventral entry point
- largest blood vessel on surface of retina
SLIDE 8
MAJOR VESSELS AVOID HIGH NERUON DENSITIES (WHEN THEY EXIST)
FAT-TAILED DUNNART
OPPOSSUM OR RAT
RETINAL GANGLION CELLS VS BLOOD VESSELS
FAT-TAILED DUNNART -
“Area centralis and visual streak”
OPPOSSUM OR RAT -
“weak or no specialisation”
SLIDE 8- LABEL AND DRAW
Summary of non-mammalian vertebrates: 2
examples of the vertebrates 4
- Everyone has choroid (back)
- Retinal vessels vary (front)\
examples:
- teleost fish
- amphibians
- reptiles
- birds
(*Concus capillaris not pleated/folded; #pecten is folded)
slide 9
Vertebrates (4) - explain their retinal vessels type and choroid
- teleost fish - HYALOID VESSELS - Choroid at back
- amphibians - HYALOID VESSELS - Choroid at back
- reptiles - CONCUS CAPILLARIS - Choroid at back
- birds - PECTEN - Choroid at back
(*Concus capillaris not pleated/folded; #pecten is foleded)
What is Fovea?
Why is fovea like a pit?
The fovea centralis is a small, central pit composed of closely packed cones in the eye.
It is located in the center of the macula lutea of the retina
The fovea is responsible for sharp central vision (also called foveal vision), which is necessary in humans for activities for which visual detail is of primary importance, such as reading and driving.
The fovea is surrounded by the parafovea belt and the perifovea outer region
The foveal pit is a zone where the inner retinal tissue, including the vasculature, is pushed to one side, leaving a clearer optical zone in the central foveola.
Moreover, inner retinal layers are laterally displaced, resulting in a concave depression called foveal pit
