Ear

Question 1

What gives rise to the internal ear?

Answer 1

Otic placode

Develops first

Question 2

What gives rise to the middle ear?

Answer 2

1 and 2 pharyngeal arches (ossicles) and 1st pharyngeal pouch for lining of tympanic cavity and pharyngotympanic tube

Question 3

What gives rise to the external ear?

Answer 3

1 pharyngeal arch

auricular hillocks

Question 4

What week does the ear begin developing?

Answer 4

Week 4 (just like eye)

Question 5

What are the direct derivatives of the otic placode?

Answer 5

Otic placode (ectoderm) forms the otic pit and then invaginates to form the Otic vesicle, which will become the membranous labyrinth

Question 6

What are the regions of the otic vesicle?

Answer 6

Dorsal utricluar part- endolymphatic ducts, utricles, semicircular ducts
Ventral saccular part- saccule and cochlear ducts (which will grow into a spiral and then the organ of corti differentiates from it)

Question 7

What tissue gives rise to the spiral and vestibular ganglia and the sensory nerves?

Answer 7

neuroectoderm

Question 8

What forms the cartilage of the inner ear?

Answer 8

Mesenchyme around otic vesicle (otic capsule)

Question 9

Major events of week 25

Answer 9

ossification of otic capsule complete, bony labrythne is fully formed and adult sized
Ossification of ossicles

Question 10

What arch does the malleus and incus come from?

Answer 10

Pharyngeal arch 1 (merkels) *NC

Question 11

What arch does stapes come from?

Answer 11

Arch2 *NC

Question 12

Where is tensor tympani from?

Answer 12

Arch 1, mesoderm

Question 13

What is stapedius from?

Answer 13

Arch 2, mesoderm

Question 14

Where is the external acoustic meatus derived from?

Answer 14

1st pharyngeal cleft/groove, surface ectoderm

Question 15

What composes the tympanic membrane?

Answer 15

Inner- endoderm
Middle- mesoderm (mesenchyme)
outer- ectoderm

Question 16

Explain the 6 auricular hillocks

Answer 16

1-3- Arch 1- they make up the tragus, helical crus, and helix
4-6- Arch 2- they make up the anti helix, anti helix, and antitragus

**Mesenchyme, all surrounding pharyngeal groove/cleft 1

Question 17

What causes embryo sensory deafness?

Answer 17

Inner ear or nerve issues, otic placode or neuroectoderm

cochlear implant

Question 18

What causes embryo conduction deafness

Answer 18

External or middle ear issues, arch 1 and 2, pouch 1, cleft 1

Question 19

What can be caused by accessory auricular hillocks?

Answer 19

Auricular appendage (skin tag)

Question 20

What is anotia?

Answer 20

Absence of auricle, failure of mesenchyme to proliferate

Question 21

What is microtia?

Answer 21

small auricle, usually associated with atresia of external acoustic meatus (cleft 1)

Question 22

What is a pre auricular cyst?

Answer 22

Narrow tubes or shallow pits anterior to auricle.

Incomplete fusion of auricular hillocks or defective closure of the first part of the 1st pharyngeal cleft