Lecture 14: Embryology of the Eye Flashcards

1
Q

Growth factors bind to

A

receptor sites on target cells

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2
Q

receptor sites on target cells control what

A

normal development by modulating proliferation, migration, and
differentiation

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3
Q

One particular gene that appears to be important in the

development of ocular structures is the

A

Pax-6 gene

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4
Q

3rd week of embryonic development: three primary germ layers have formed the embryonic plate

A
  • Ectoderm
  • Mesoderm
  • Endoderm
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5
Q

what layers will take part in the developing ocular

structures

A

Only ectoderm and mesoderm

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6
Q

Ectoderm

A

outer layer

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7
Q

mesoderm

A

middle layer

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8
Q

endoderm

A

inner layer (NOT INVOLVED)

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9
Q

what layer thickens to form neural plate

A

ectoderm

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10
Q

Neural Plate gives rise to

A

CNS and eye

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11
Q

Longitudinal groove in neural plate

A

neural groove

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12
Q

Lateral edges of neural groove are brought closer

together and are called

A

nural folds

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13
Q

Neural folds fuse to give

A

neural tube (ectoderm)

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14
Q

Neural tube surrounded by

A

mesoderm

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15
Q

Mesoderm covered dorsally by surface

A

ectoderm (surface and neural)

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16
Q

As neural folds move towards one another

A

neural crest cells differentiate

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17
Q

NCs take up a position in mesoderm between

A

neural tube and surface ectoderm

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18
Q

Mesenchyme =

A

collective term that includes both neural crest cells + mesoderm

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19
Q

As neural tube is closing

A

optic pits form on both sides of forebrain

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20
Q

Optic pits form a

A

diverticulum

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21
Q

diverticulum extend laterally from forebrain and are called

A

optic vessels

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22
Q

– For a brief time the optic vesicles are in contact with the

A

surface ectoderm

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23
Q

Soon neural crest cells situate themselves in

A

mesoderm between the optic

vesicle and surface ectoderm

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24
Q

What happens if inferior optic fissure does not zip

completely?

A
  • Uveal Coloboma with Optic
    Nerve involvement
  • Iris Coloboma “Key Hole
    Pupil”
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25
Coloboma
Incomplete closure of the optic fissure may affect the developing optic cup or stalk, resulting in an inferior nasal defect in the optic disc, retina, ciliary body, or iris.
26
coloboma and can vary from | a slight notch to a
large wedge like defect.
27
Colobomas affecting the sensory retina and RPE | also involve
the choroid because its differentiation | depends on an intact RPE layer
28
optic cup resembles a
sphere that has collapsed onto itself
29
how many layers is the optic cup composed of
2 layers (inner and outer) arranged apex to apex
30
The optic vesicle was in contact with the surface ectoderm. It pulls back inducing
lens placode to | form
31
Center of the placode | elongates forming
lens pit
32
Pit invaginates until
forms hollow circular | structure, lens vesicle
33
lens vesicle is composed of how many cell layers? surrounded by?
Composed of a single layer of cells surrounded by a basal lamina (future lens capsule)
34
lens vesicle takes up position in
future vitreous chamber
35
lens vesicle is derived from
surface ectoderm
36
Makes sense because structures derived from surface ectoderm continuously
form throughout life (I.e. skin)
37
All Secondary Lens Fibers are derived from
the Anterior Lens Epithelium
38
Six crescent fibers are laid down equidistant in a
growth shell
39
Subsequent fibers are laid down and follow the pattern to give rise to an
Anterior upright Y-suture and a Posterior Inverted Y-suture.
40
The spectrum of lens opacities that can result from problems during lens development range from
pinpoint densities having no effect on vision to | significant opacities causing extensive loss of vision
41
If the tissue near the developing lens fails to induce the lens fibers to elongate and pack together in an orderly way,
the lens fibers will be misaligned, forming a | cataract of the primary fibers.
42
Hyaloid Vasculature gives rise to
Central Retinal Artery and Vein
43
Hyaloid Vasculature may leave its mark on the
lens and optic nerve (Bergmeister's papilla and Mittendorf's dot)
44
Choroid is induced by RPE to form
from Mesenchyme
45
As the optic cup grows, the vitreous cavity is filled with
fibrillar material that is secreted by embryonic retina, lens, and hyaloid vasculature which is referred to as primary vitreous
46
Cup increases in size, secondary vitreous develops from
retina and degenerating | hyaloid = secondary vitreous (what we now have).
47
Secondary vitreous | pushes primary vitreous
anteriorly
48
Funnel-shaped tube remnant of
hyaloid vasculature. (Cloquet’s canal is left in the middle)
49
Optic Stalk is
the precursor
50
Inferior optic fissure invaginates forming a
two-layered stalk
51
Outer layer gives | rise to
neuralglial sheath that | surrounds optic nerve.
52
The inner layer of the optic nerve is destroyed by
apoptosis to make way | for axons of the retinal ganglion cells.
53
RPE forms from
outer layer of optic cup
54
what layer is the first layer of the retina to differentiate
RPE
55
what is the first visible pigmentation in the embryo!
RPE
56
Apex faces
retina
57
basal surface faces
Bruch’s membrane.
58
retina forms
inner layer of optic cup
59
Photoreceptors continue to develop
well after birth to increase resolution and sensitivity of the visual system
60
Macula first develops as an area of
increased ganglion cell density lateral to the optic disc
61
Inner retinal elements become displaced as
cones increase packing density
62
Henle’s layer (PR inner fibers) develops
obliqueness in fovea
63
what is the last portion of retina to fully develop
fovea
64
Lens vesicle induces the formation
cornea
65
Corneal epithelium is derived from the
surface ectoderm.
66
Stroma from
mesenchyme
67
Corneal endothelium from
neural crest cells
68
Sclera and EOMs originate from
MESENCHYME outside the optic cup
69
Sclera will envelop the developing
choroid
70
Connective tissue fibers will pass through the | scleral foramen and optic nerve fibers to form the
lamina cribrosa.