Ear Development

Question 1

When is the critical period for embryological development of the year?

Answer 1

B/w weeks 4 and 8

Question 2

When does development of the ear occur?

Answer 2

Between wks 4 and 20

Question 3

The medial part of the external ear came from what pharyngeal arch?

Answer 3

1st

Question 4

The lateral part of the external ear came from what pharyngeal arch?

Answer 4

2nd

Question 5

The mesenchymal swellings located within the pharyngeal arches are known as what?

Answer 5

Auricular hillocks

Question 6

What are the cells that migrate and pull the surface ectoderm around to form the external ear?

Answer 6

Neural crest cells of the auricular hillocks

Question 7

Auricular skin tags that may contain cartilage are a result of what?

Answer 7

Abnormal migration of surface ectoderm and neural crest cells

Question 8

Abnormal or absent migration of the NCCs and auricular hillocks can result in what disorders?

Answer 8

Anotia

Microtia

Question 9

What embryonic layer does the meatal plug arise from?

Answer 9

Surface ectoderm - 1st pharyngeal cleft

Question 10

What embryonic layer does the inner ear arise from?

Answer 10

Surface ectoderm

Question 11

What week does the inner ear begin to form?

Answer 11

Week 4

Question 12

What embryonic structure gives rise to the membranous labyrinth?

Answer 12

Otic vesicle

Question 13

Development of the utricle is dependent on what transcription factors?

Answer 13

DLX5 and DLX6

Lateral canal dependent on OTX1

Question 14

What does the dorsal side of the otocyst give rise to?

Answer 14

Semicircular ducts and ampullae

Macula of utricle

Endolymphatic duct and sac

Question 15

What does the ventral side of the otocyst give rise to?

Answer 15

Cochlear duct

Ductus reuniens

Maccula of saccule

Organ of Corti

Question 16

What structure connects the cochlea to the vestibular apparatus?

Answer 16

Ductus reuniens

Question 17

What is the embryonic layer that gives rise to the hair cells of the inner ear?

Answer 17

Surface ectoderm

Question 18

Where are hair cells located in the inner ear?

Answer 18

Ampullae of semicircular canals

Macula of utricle

Organ of Corti (cochlea)

Question 19

What CN is responsible for innervation to the inner ear?

Answer 19

CN VIII - Vestibulocochlear

Question 20

What are the embryonic contributions to the vestibular ganglion?

Answer 20

Neural crest cells and surface ectoderm

Question 21

What is the embryonic contribution to the spiral (cochlear ganglion)?

Answer 21

Surface ectoderm

Question 22

What structures does the perilymphatic duct provide passage between?

Answer 22

Subarachnoid space to inner ear

Question 23

What is the ion content of perilymph?

Answer 23

High Na

Low K and ptn

(Similar to CSF)

Question 24

What is the ion content of endolymph?

Answer 24

High K and ptn

Low Na

(Similar to ICF)

Question 25

What embryonic layer does the bony labyrinth arise from?

Answer 25

Mesoderm

Question 26

In what week are the vacuoles of the bony labyrinth distinguishable as the scala vestibuli and scala tympani?

Answer 26

Week 8

Question 27

In what week do the vacuoles of the bony labyrinth begin to form?

Answer 27

Week 6

Question 28

What suspends the cochlear duct within the bony labyrinth and attaches it to the wall?

Answer 28

Spiral Ligament

Question 29

What embryonic layer forms the tubotympanic recess?

Answer 29

Endoderm - 1st pharyngeal pouch

Question 30

What bones of the middle ear arise from the 1st arch NCC?

Answer 30

Malleus and Incus

Question 31

The stapes bone arises from what arch? What is the embryonic origin?

Answer 31

2nd arch Neural crest

Question 32

What embryonic layer does the epithelium covering the ossicles arise from?

Answer 32

Endoderm

Question 33

What are the embryonic layers making up the tympanic membrane?

Answer 33

Ectoderm - from 1st pharyngeal cleft Mesoderm Endoderm - from 1st pharyngeal pouch

Question 34

What pharyngeal arch does the tensor tympani M. arise from? What embryonic layer?

Answer 34

1st Pharyngeal arch Mesoderm

Question 35

What pharyngeal arch does the Stapedius M. arise from? What embryonic layer?

Answer 35

2nd pharyngeal arch Mesoderm

Question 36

What part of the fetal ear is affected if there is a maternal Rubella infection?

Answer 36

Inner ear - Spiral Organ/Organ of Corti defects