Eye and Ear Embryology

Question 1

4 sources that contribute to eye development

Answer 1

neuroectoderm of the brain (retina)

surface ectoderm of the head (lens)

mesoderm

NCC

Question 2

when do optic grooves appear in cranial neural folds?

Answer 2

week 4

Question 3

folds of optic grooves fold to form _______

Answer 3

optic vesicles

Question 4

optic vesicles’ connections with forebrain thin to form _______ and induce overlying surface ectoderm to thicken, forming ________

Answer 4

optic stalks

lens placodes

Question 5

lens placodes invaginate to form _______ which then fuse to form _______ and separate from surface ectoderm

Answer 5

lens pits

lens vesicles

Question 6

optic vesicles invaginate for form _______

Answer 6

optic cups

Question 7

why are meninges on the optic nerve?

Answer 7

because it is an outpouching of the forebrain

Question 8

the retina develops from the ______

Answer 8

optic cup

Question 9

outer layer of optic cup becomes

Answer 9

retinal pigment epithelium

Question 10

inner layer of optic cup becomes

Answer 10

neuroepithelium of retina

Question 11

neuroepithelium of retina contains

Answer 11

photoreceptor cells

Question 12

what is a detached retina

Answer 12

when two layers of retina separate

Question 13

two lens fibers

Answer 13

primary - from columnar cells

secondary - from cuboidal cells and along rim of lens

Question 14

choroid, sclera, and ciliary body develop from

Answer 14

optic cup

Question 15

what is the choroid

Answer 15

inner, vascular layer of mesenchyme

- extension forms ciliary body

Question 16

what is the sclera

Answer 16

outer, fibrous layer of mesenchyme

Question 17

iris develops from

Answer 17

rim of optic cup

Question 18

muscles of iris (2)

Answer 18

dilator pupillae

sphincter pupillae

Question 19

muscles of iris derived from

Answer 19

neuroectoderm of optic cup

Question 20

cornea formation induced by

Answer 20

lens vesicle

Question 21

3 sources of cornea

Answer 21

external corneal epithelium derived from surface ectoderm

mesenchyme continuous with developing sclera

NCC from optic cup

Question 22

jelly-like substance that gives shape to eye found in posterior segment

Answer 22

vitreous humor

Question 23

how do eyelids develop?

Answer 23

NCC proliferate and folds of skin grow over cornea

Question 24

when do eyelids adhere together and when do they un-fuse

Answer 24

week 10

26+ weeks

Question 25

failure of closure of the retinal fissure that may be inherited - leads to “keyhole” appearance of iris

Answer 25

Coloboma of iris

Question 26

abnormal development of sclerus venous sinus caused by an imbalance between aqueous humor production and its outflow

Answer 26

congenital glaucoma

Question 27

opaque lens

genetic

Answer 27

congenital cataracts

Question 28

virus that can cross placental membrane and cause glaucoma and cataracts

Answer 28

rubella

Question 29

dystrophy of levator palpebrae superior muscle

Answer 29

congenital ptosis of eyelid

Question 30

small notch in eyelid devoid of eyelashes

Answer 30

coloboma of eyelid

Question 31

external acoustic meatus develops from

Answer 31

1st pharyngeal groove

Question 32

what is the meatal plug

Answer 32

cells of 1st pharyngeal groove form solid epithelial plate - this degenerates and becomes a cavity

Question 33

mesenchyme proliferates from first and second arches to form

Answer 33

auricle

Question 34

describe movement of auricle during development

Answer 34

initially in neck and is pushed superiorly by mandible development

Question 35

middle ear develops from

Answer 35

tubotympanic recess from 1st pharyngeal arch

Question 36

proximal part of tubutympanic recess forms _______

distal part forms _________

Answer 36

pharyngotympanic tube

tympanic cavity

Question 37

development of internal ears (with arrows)

Answer 37

otic placodes –> otic pit –> otic vesicle

• • dorsal region of otic vesicle –> endolymphatic duct, utricle, and semicircular
• • ventral region of otic vesicle –> saccule and cochlear duct

Question 38

earliest of 3 parts of ear to develop (happens in week 4)

Answer 38

internal ear

Question 39

ventral saccular part of otic vesicle coils and grows to form ________

_______ differentiates from cells in wall of the cochlear duct

CN VIII cells migrate along coils to form ______ with cells that terminate on hair cells

Answer 39

membranous cochlea

spiral organ

spiral ganglion