eye embryology (FUNK)

Question 1

what is the first part of the eye to form

Answer 1

neural tunic (retina and optic nerve)

Question 2

what is special about CN II

Answer 2

fully invested in meninges

only CN that is invested in meninges and is in the same fascial sheath as the brain

Question 3

congenital retinal detachment

Answer 3

Congenital retinal detachment occurs when the inner and outer layer of optic cup fail to fuse; separation of pigmented and neural layers of retina (will result in blindness if not reattached).
this is bad b/c the rods/cones need the pigmented epithelium to survive (metabolic, blood supply, structural support)

-cat litter parasites- so have prego moms avoid cat litter

Question 4

acquired retinal detachment

Answer 4

trauma, infectious agents
separation is along the same plane (pigmented epithelium and rods/cones)

can lead to blindness

Question 5

structures of the eye are derived from what 3 sources

Answer 5

neural ectoderm (optic vesicles)
surface ectoderm
mesenchyme

Question 6

what is neural ectoderm (optic vesicles) formed from

what occurs in the development of the optic vesicles

Answer 6

a. Derived from evaginations of the forebrain neuroectoderm
b. Meninges carried along with developing eye.
c. Optic vesicles invaginate on themselves to form a double-walled optic cup.
d. Optic cup retains connection to forebrain at optic stalk.
e. Choroid fissure forms on ventral surface of optic cup – carries hyaloid vessels
f. Forms retina, optic nerve

Question 7

what is the lens formed from

Answer 7

surface ectoderm

lens placode –> lens vesicle
forms the lens

Question 8

what is the optic cup

Answer 8

evagination of diencephalon

Question 9

what does the outer layer of the optic cup form

Answer 9

pigmented epithelial layer of retina

Question 10

what does the inner layer of the optic cup form

Answer 10

neural layers (rods/cones, bipolar, and ganglion cells) of retina

Question 11

what does the optic stalk form

Answer 11

optic nerve CN II

Question 12

does the choroid fissure close?

Answer 12

yes week 7

Question 13

what does the outer layer of the mesenchyme form

Answer 13

fibrous (sclera, cornea)

Question 14

what does the inner layer of the mesenchyme form

Answer 14

vascular layer (choroid, iris, ciliary body)

Question 15

what is the outer portion of the iris and ciliary body derived from

Answer 15

vascular mesenchyme surrounding optic cup

Question 16

what is the inner portion of the iris and ciliary body formed from

Answer 16

optic cup (no neural elements)

Question 17

why are most infants born with blue-gray eyes

Answer 17

due to lack of melancocytes in anterior portion of iris

melanocytes migrate into the anterior iris in the first 6-10 months

Question 18

what is the iridopupillary membrane

Answer 18

vascular structure which originally separates the anterior and posterior aqueous chambers

degenerates around week 15

Question 19

what happens when the iridopupillary membrane doesn’t degenerate

Answer 19

leads to congenital atresia of the pupil.

Question 20

what is coloboma

Answer 20

results from a failure of the choroid fissure to fuse during the 7th week of development (may also involve retina).

Question 21

how do the aqueous and vitreous chambers of eye form

Answer 21

eye chambers form in areas of cell death within the eyeball

vitreous humor is likely derived from neural crest cells

Question 22

what is the lens derived from

Answer 22

lens vesicle (surface ectoderm)

Question 23

what is congenital aphakia

Answer 23

agenesis of lens placode (no formation of the lens placode)

Question 24

what are the extra ocular eye muscles formed from

Answer 24

H. Extrinsic eye muscles form from mesoderm of myotomes (paraxial mesoderm) and all have a GSE component !

NOT pharyngeal arches