19. Developmental Anatomy: Neural Crest, Eye, Ear

Question 1

Where do neural crest cells come from?

Answer 1

Lateral edge of neural ectoderm

Question 2

Where do neural crest cells migrate once the neural fold is closed?

Answer 2

Into mesenchyme

Enter mesoderm

Question 3

Which disease is due to the failure of neural crest cells to migrate into the bowel wall?

Answer 3

Hirschsprung’s disease

Question 4

Why are there no bowel reflexes in Hirschsprung’s disease?

Answer 4

No parasympathetic plexus

Question 5

Which parts of the bowel are most affected by Hirschsprung’s?

Answer 5

Sigmoid colon

Rectum

Question 6

What does Hirschsprung’s disease present as?

Answer 6

Constipation
Vomiting
Abdominal distension

Question 7

What is the first sign of eye development on day 22?

Answer 7

Pair of shallow grooves at the side of the forebrain

Question 8

What are the outpocketings of forebrain known as?

Answer 8

Optic vesicles

Question 9

What causes the changes needed for lens formation?

Answer 9

Vesicles come in contact with surface ectoderm

Question 10

What is the optic cup formed by?

Answer 10

Invagination of the optic vesicle

Question 11

What are the layers of the optic cup separated by?

Answer 11

Intraretinal space

Question 12

What gap allows the hyaloid artery to reach the inner chamber of the eye?

Answer 12

Choroid fissure

Question 13

What will eventually form the pupil?

Answer 13

Fused lips of the choroid fissure, which form a round opening in the optic cup

Question 14

What forms the lens placode?

Answer 14

Elongated cells of the surface ectoderm

Question 15

What happens at the canal of Schlemm?

Answer 15

Aqueous humour drains into venous circulation

Question 16

What are the retina, iris and optic nerve derived from?

Answer 16

Neuroectoderm

Question 17

What are the lens and corneal epithelium derived from?

Answer 17

Surface ectoderm

Question 18

What does the mesoderm between the neuroectoderm and surface ectoderm form?

Answer 18

Fibrous and vascular coats of the eye

Question 19

What are the choroid, sclera and corneal endothelium derived from?

Answer 19

Neural crest cells

Question 20

What is a coloboma?

Answer 20

Choroid fissure fails to close

Question 21

What are the causes of congenital cataracts?

Answer 21

Genetics

Maternal rubella

Question 22

What is cyclopia?

Answer 22

Fusion of eyes due to loss of midline tissue

Question 23

What is the first sign of ear development?

Answer 23

Thickening of surface ectoderm on each side of rhombencephalon (Otic placodes)

Question 24

What are otic placodes known as once they invaginate?

Answer 24

Otic or auditory vesicles

Question 25

What does each otic vesicle divide into?

Answer 25

Ventral and dorsal parts | Differentiation forms ganglion cells for vestibulocochlear ganglia

Question 26

What is derived from the ventral part of the otic vesicle?

Answer 26

Saccule and Organ of Corti

Question 27

What is derived from the dorsal part of the otic vesicle?

Answer 27

Utricle Semicircular canals Endolymphatic duct

Question 28

What is the collective names for the structures formed by the ventral and dorsal vesicles?

Answer 28

Membranous labyrinth

Question 29

What happens to the otic vesicle in the 4th week?

Answer 29

Detaches from surface ectoderm

Question 30

What role do neural crest cells have in the ear?

Answer 30

Form bony labyrinth in temporal bone

Question 31

What forms the perilymphatic space?

Answer 31

Connective tissue closest to the membranous labyrinth degenerates

Question 32

What is the tympanic cavity derived from?

Answer 32

1st pharyngeal pouch

Question 33

What comes from the distal part of the 1st pharyngeal pouch?

Answer 33

Tubotympanic recess > primitive tympanic cavity

Question 34

What comes from the proximal part of the 1st pharyngeal pouch?

Answer 34

Eustachian tube

Question 35

Which pharyngeal arch do the malleus and incus come from?

Answer 35

1st

Question 36

Which pharyngeal arch does the stapes come from?

Answer 36

2nd

Question 37

What is the tympanic membrane made up of?

Answer 37

Ectodermal epithelium lining at bottom of auditory meatus and tympanic cavity Connective tissue

Question 38

What is the filling of the external auditory meatus with ectodermal cells called?

Answer 38

Meatal plug

Question 39

What does the pinna develop from?

Answer 39

6 auricular hillocks surrounding the 1st pharyngeal cleft