Retinal Development Flashcards
Where do the neural folds and groove originate on
Embryonic disc
What is formed when the neural folds and groove get zipped
The neural tube
What makes up the inner tube of the embryo
The neural tube
What makes up the outer tube of the embryo
Surface ectoderm
That liters between the 2 tubes of the embryo
Mesenchyme
What are the 2 evaginations that form off the cranial portion of the neural tube
Optic vesicles
What are the optic vesicles made of
Neural ectoderm
The optic vesicles will elongate and form the
Optic stalk
When the optic vesicles encounters the surface ectoderm what happens
It will fold in (invaginate)
What does invagination of the surface ectoderm form
Optic cup
As the optic cup folds in on itself, the back of the cup comes into contact with the layer from the front of the cup. This creates what relationship
Apex to apex
What is the space that forms between the inner and outer layers of the optic cup
Intraretinal space
What s the most posterior layer of the optic cup (outer layer)
RPE
What is the inner layer of the optic cup
Neural retina
The anterior outer layer is what tissue
Pigmented ciliary epithelium
The anterior inner layer Is what tissue
Nonpigemnted epithelium
The most anterior outer layer is what tissue
Anterior iris epithelium
What tissue is the most anterior inner layer
Posterior iris epithelium
What is the first layer of the retina to differentiate
The RPE
Cellular structures and melanosomes begin to appear in the outer layer of the optic cup, and pigmentation of the retinal epithelium occurs when
Week 3-4
What happens to the RPE at week 6
The RPE is 1 cell layer thick
Cuboidal-columnar shape
Between weeks 4-6 the cells of the inner layer of the optic cup do what
Proliferate and form 2 zones
The neural retina subdivides into 2 areas in what week of development
4-6
What is the outer layer of the neural retina
Proliferation zone
What is the inner zone of the neural retina
Marginal zone
What is layer of the retina is formed at weeks 4-6
What is its function
Basal lamina (will become the ILM)
Separates the retina from the vitreous
At week 7, cell migration occurs and forms these
Inner and outer neuroblastic layers
What lies between the inner and outer neuroblastic layers
Transient fiber layer of Chievitz
Differentiation of the neural retinal cells begins where
In the central retina and proceeds to the periphery
Formation of the neuroblastic layers is complete by this month
3rd month
Inner neuroblastic layer development
- Ganglion cells migrate and form a layer close to the basement membrane
- Biomolecular agents guide atonal growth toward termination in the lateral geniculate nucleus
- Muller cells develop at the same time. Bodies of the Muller and amacrine cells remain in the inner neuroblastic layer but move toward the sclera
Outer neuroblastic layer development
- Bipolar cells migrate from outer neuroblastic layer and settle near the Muller and amacrine cells
- Horizontal cells follow
- Diner layer of Chievitz is gradually obliterates by this move of bipolar and horizontal cells
- Photoreceptor cells reman in the outer neuroblastic layer
By week 23 the photoreceptors are aligned along the outer side of the inner layer of the optic cup and _______ appear between them
Adhering jxns
What do the adhering junctions form eventually
The ELM
What are the last cells of the neural retina to differentiate
When does this occur
Photoreceptor cells
5th month
What photoreceptor differentiates first?
Second?when?
1st: cones
2nd: rod (7th month)
The inner segment creates a protuberance that embeds in teh RPE and continues to grow and form what?
When?
Cilium
Week 24-25
Where do the horizontal, bipolar, amacrine, and Muller cells develop
Inner nuclear layer
What are the inner and outer plexiform layers filled with
Neuronal processes
The fiber s of the Muller cells appear and extend to the basal lamina, forming this
Primitive internal limiting membrane
What is the function of the Muller cells
Provide scaffolding for cell development and appears to be involved with guiding the direction of atonal fiber growth
What develops first cone pedicles or rod spherules?
Cone pedicles
Photoreceptor synapses with ________ cells are established before the outer segments are completed
Bipolar cells
What is well established by month 5
Ganglion cell layer
Because the retinal development is more advanced centrally than peripherally what happens to the ganglion cells
Ganglion axons from the periphery must take an arched route above and below the macular area to reach teh nerve ahead
What is teh line of deviation at the horizontal temporal meridian Called
Horizontal raphe
What occurs to the retinal cells in the 5th month
Reduction of retinal cells by apoptosis
What occurs to the retinal cells at month 6
No further mitosis
Retinal growth continues because of cell differentiation, growth, and maturation
When do the cones differentiate
6th month
Why is the fovea thicker
There is a dense accumulation;action of nuclei (up to 9 rows of ganglion cells)
What are the 3 stages of foveal development
- Displacement of inner retinal component form depression
- Migration of photoreceptors toward the center, increases cone packing
- Maturation of photoreceptors
When do the ganglion cells and inner nuclear cells move to the periphery of the macula
7th
How many layers are there of the ganglion cells and inner nuclear layer at birth
1
At 4 months pb the ganglion and INL are displaced to sloping walls of the fovea, leaving what as the only neural cell bodes in the center of the depression
Cones of the outer nuclear layer
What is the foveola
Retinal area of sharpest VA
What is the last region to mature
Foveola
Before birth the rod-free area is large compared to adults but becomes narrower with migration of the cones centrally, increasing cone density
Foveola
What is the cone population in the foveola in 1 week old infant
18
What is the cone population in the 4-5 y.o of the foveola
42
The cone inner fibers elongate and adopt what orientation
Why does this occur?
Oblique orientation
So they can synapse with the cells of the INL
What continues to develop during the first few years of life
Outer segment
Inner fiber lengthens
What can newborns see
Changes in brightness
Non-moving vs moving objects
Follow moving objects
What is the VA of newborn
20/800-20/200
What is the VA of 2 mo old
20/150
What is the VA of a 4 mo old
20/60
What is the VA of 6 mo old
20/20
Look at slide 35
Development flow chart
The foveal depression continues to deepen until what age (as cells move toward the macular periphery)
15 months pb
