Development And Histology Of The Ear

Question 1

Development of the internal ear

Answer 1

Begins in week 3 (20 days roughly)

- neural epithelium forms the otic placode and otic vesicles which forms the inner ear from otic pits

Question 2

What is the purpose of delmaninating neuroblasts

Answer 2

Give rise to bipolar primary afferent neurons of CN 8

These are epithelium cells that come off the otic vesicle directly

Question 3

What 3 parts does the otic capsule differentiate into?

Answer 3

Scala vestibuli

Scala tympani

Cochlear duct w/ spiral organ

Question 4

Development of the middle and external ear

Answer 4

Are derived from the first and second pharyngeal arches

• internal auditory meatus is from the first pharyngeal groove
• middle ear is mostly from the first pharyngeal pouch

Bones are derived from both the 1st and 2nd arch

• incus and malleolus = 1st arch
• stapes = 2nd arch

Question 5

Auricular hillocks and what part of the external ear they produce

Answer 5

1-3

• produced from the 1st pharyngeal arch
• form the tragus, concha and fossa of helix

4-6

• produced from the 2nd pharyngeal arch
• form the fossa of antihelix, anti tragus and anti helix

Question 6

1st arch syndrome

Answer 6

1st pharyngeal arch fails to from properly

• causes damage to the external auditory meatus or middle ear
• leads to conductive impairments

Question 7

Sensorineural impairments

Answer 7

Typically arise from developmental disruptions for he internal ear/ CN 8 or brainstem I nuclei

Common with teratogenic agents used in week 7-9