embryology of the eye and ear

Question 1

development of the outer ear
Pinna- ?
External auditory meatus- ?
Tympanic membrane- ?

Answer 1

• Pinna arises from fusion of six auricular hillocks
• external auditory meatus is ectoderm of first pharyngeal cleft
• tympanic membrane- “inner layer- from endoderm”, middle layer- from mesoderm; outer layer -ectoderm

Question 2

development of the middle ear:

Answer 2

Eustachian tube–> from first pharyngeal pouch endoderm
- malleus and incus–> 1st pharyngeal arch
- stapes- 2nd pharyngeal arch mesoderm

Question 3

development of the inner and membranous labyrinth:

Answer 3

• membranous labyrinth: derived from ectodermal invagination from otic placode
• bony labyrinth- from mesoderm

Question 4

eye:
when does choroid fissure, give rise to pupil, close

Answer 4

week 7

Question 5

eye:
ectoderm cells elongate, form _______

Answer 5

lens placode

Question 6

eye development:

lens placode invaginate, forms _____

Answer 6

lens vessicle