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MBBS2/Anatomy~HEAD & NECK > Development of the eye > Flashcards

Development of the eye Flashcards

1
Q

eyes are derived from what

A
  1. surface ectoderm
  2. lateral neuroectodermal walls of the embryonic diencephalon
  3. mesenchyme
  4. neural crest cells
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2
Q

what do you see at the beginning of the 4th week (D22)

A

-a pair of optic grooves/sulcus appear on the sides of the forebrain
-as the neural tube fuses :
1. the optic grooves evaginate to form optic vesicles
2. and the optic vesicles become continuous with the cavity of the forebrain

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3
Q

what induces the optic grooves to evaginate to form the optic vesicles

A

mesenchyme adjacent to the brain

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4
Q

during the mid of the 4th week what happens to the optic vesicles as they expand

A

their connections constrict to form optic stalks

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5
Q

as the optic vesicles contact the surface ectoderm what happens (mid of 4th week)

A

-it induces the surface ectoderm to thicken and form lens placodes

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6
Q

what happens to the lens placodes

A

-they evaginate and sink into the surface ectoderm forming lens pits
-the edge of the lens pits then later fuse to form the lens vesicle
-the lens vesicle then later pinches off the surface ectoderm

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7
Q

what are the layers of the optic cup

A

inner layer- neuroepithelium (neural retina)
outer layer- retinal pigment epithelium
intraretinal space

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8
Q

what happens as the lens develops

A

-the optic vesicles invaginate to form the double layered optic cup due to the lens vesicles invaginating into the optic vesicle/pinching off the surface ectoderm
-retinal fissures/optic fissures develop on the ventral surface of the optic cup due to incomplete folds in the inferior portion of the optic cup and stalk

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9
Q

retinal/optic fissures form a passage way for what

A

hyaloid artery and vein (branch of the ophthalmic artery)

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10
Q

what happens when the optic fissures fuse

A

the hyaloid artery and vein are enclosed within the primordial optic nerve (hyaloid system is incorporated within the eye)

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11
Q

what does the hyaloid artery and vein later become

A

the central artery and vein of the retina

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12
Q

when does the hyaloid artery enter the optic fissure

A

5th week

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13
Q

whats a coloboma

A

its when there is failure of closure of the optic/choroidal fissure

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14
Q

what does a coloboma look like

A

it gives a key hole appearance in the iris

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15
Q

whats the position of the coloboma

A

the infero-nasal quadrant (which is reflective of the location of the optic fissure during development)

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16
Q

where does the retina develop from

A

walls of the optic cup

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17
Q

what forms the retina pigment epithelium

A

the outer thin layer of the optic cup

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18
Q

what forms the neural layer of the retina

A

the inner thick layer of the optic cup

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19
Q

during embryonic/fetal period what separates the 2 layers of the retina

A

the intraretinal space

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20
Q

what eventually happens to the 2 layers of the retinal that are separated by the intraretinal space

A

they loosely fuse

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21
Q

what causes the inner layer of the optic cup to form the thick neuroepithelium- which later then forms the neural retina (photoreceptor cells) , bipolar and ganglion cell bodies

A

the induction by the lens

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22
Q

what is incomplete at birth with the axons given off by the ganglion cells to form the optic nerve

A

myelination

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23
Q

what is the cavity of the optic stalk filled with

A

axons of the optic nerve

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24
Q

what happens when the outer and inner layers of the optic cup fail to fuse

A

congenital detachment of the retina

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25
Q

what is the ciliary body

A

its a wedge shaped extension of the choroid

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26
Q

what does the medial surface of the ciliary body do

A

it projects towards the lens and forms ciliary processes

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27
Q

where is the pigmented portion of the ciliary epithelium derived from

A

the outer layer of the optic cup

28
Q

the pigmented portion of the ciliary epithelium is continuous with what

A

the retinas pigmented epithelium

29
Q

the non pigmented portion of the ciliary epithelium is an anterior prolongation of what

A

the neural retina epithelium

30
Q

where does the ciliary muscle develop from

A

mesenchyme located at the edge of the optic cup

31
Q

what structure of the eye develops from the inward growth at the rim of the optic cup

A

iris

32
Q

what are the 2 layers of the optic cup like at the iris

A

they remain thin in that area

33
Q

the iris epithelium represents what

A

both layers of the optic cup

34
Q

the iris epithelium is continuous with the double layered epithelium of what

A

-ciliary body
-retina pigment epithelium and neural retina

35
Q

where do the dilator and sphincter pupillae muscles arise from

A

the neuroectoderm

36
Q

where does the lens develop from

A

the lens vesicle

37
Q

the lens vesicle is a derivative of what

A

the surface ectoderm

38
Q

what is the anterior wall of the lens composed of

A

cuboidal epithelium

39
Q

what does the anterior wall of the lens form

A

the subcapsular lens epithelium

40
Q

what does the posterior wall of the lens form

A

primary lens fibers which are tall columnal cells that eventually lose their nuclei

41
Q

what is the rim of the lens called

A

the equatorial zone

42
Q

what do the cuboidal cells of the equatorial one do

A

they continuously elongate lose nuclei and become secondary lens fibers

43
Q

the developing lens is invested by what

A

a vascular mesenchymal layer/ dense capillary network called the tunic vasculosa lentis

44
Q

what does the anterior part of the tunica vasculosa lentis form

A

the pupillary membrane

45
Q

what supplies the tunica vasculosa lentis

A

hyaloid artery

46
Q

what happens when the hyaloid artery degenerates in the fetal periods

A

the tunica vasculosa lentis also degenerates leaving behind a hyaloid canal

47
Q

what forms the posterior part of the tunica vasculosa lentis

A

the posterior pupillary membrane ( which covers the lens capsule)

48
Q

the tunica vasculosa grows towards what

A

the equator of the lens

49
Q

where does the anterior chamber develop from

A

the cleft like space that forms in the mesenchyme between the developing lens and cornea

50
Q

where does the posterior chamber develop from

A

the space that forms in the mesenchyme posterior to the developing iris and anterior to the developing lens

51
Q

the external corneal epithelium is derived from what

A

the surface ectoderm

52
Q

CT of mesenchyme of the cornea is derived from what and is continuous with what

A

-derived from mesoderm
-is continuous with developing sclera

53
Q

where does the corneal endothelium develop from

A

neural crest cells migrating into the cornea

54
Q

where do the choroid (inner vascular) and sclera (outer fibrous) develop from

A

condensation of the neural crest mesenchyme surrounding the optic cup

55
Q

what happens to the choroid at the rim of the optic cup

A

its becomes modified to form the ciliary processes consisting of capillary blood vessels with CT

56
Q

when do the eyelids develop

A

6th week

57
Q

the eyelids develop from what

A

-neural crest cell mesenchyme
-two folds of skin that grow over the cornea

58
Q

what do the eyelids do when developing

A

they adhere to each other in the 10 week and reopen in the 26-28th week

59
Q

what lies anterior to the cornea

A

the conjunctiva sac

60
Q

what does the surface ectoderm differentiate into

A

-lens of eye
-cornea epithelium

61
Q

what does the neuroectoderm differentiate into

A

-retina
-posterior layers of the iris
-optic nerve

62
Q

what does the mesenchyme differentiate into

A

-fibrous coat of the eye
-vascular coat of the eye

63
Q

what develops from neural crest cells in the mesenchyme

A

-choroid
-sclera
-corneal endothelium

64
Q

what is derived from the surface ectoderm

A

-lens
-epithelium of the cornea, conjunctiva and lacrimal gland and its drainage system

65
Q

what is derived from the neural ectoderm

A

-vitreous body (from neural ectoderm of the optic cup and from mesenchyme)
-epithelium of the retina, iris, and ciliary body
-sphincter pupillae and dilator pupillae muscles
-optic nerve

66
Q

what is derived from the mesoderm

A

-sclera
-stroma of the cornea, ciliary body, iris and choroid
-extra ocular muscles
-eyelids (except epithelium and conjunctiva)
-hyaloid system
-coverings of the optic nerve
-connective tissue and blood vessels of the eye, bony orbit and vitreous body

MBBS2/Anatomy~HEAD & NECK (4 decks)

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