Ear Development

Question 1

What makes up the external ear?

Answer 1

Auricle
EAM
External layer of the tympanic membrane

Question 2

What makes up the middle ear?

Answer 2

3 ossicles
Internal layer of tympanic membrane
Middle ear cavity

Question 3

What makes up the internal ear?

Answer 3

Vestibulocochlear organ

Question 4

When is the critical period for the development of the ear?

Answer 4

Weeks 4-8

But still out to wk. 20

Question 5

What is the auricle formed from?

Answer 5

PA 1 and 2

Question 6

What is the external acoustic meatus formed from?

Answer 6

PA 1 groove -ectoderm

Question 7

What is the tympanic membrane formed from?

Answer 7

PA 1 membrane (Mesenchyme, ectoderm and endoderm)

Question 8

What is the origin of the malleus?

Answer 8

PA 1

Question 9

What is the origin of the incus?

Answer 9

PA 1

Question 10

What is the origin of the Stapes?

Answer 10

PA 2

Question 11

How do the auricular hillocks develop?

What is the fate of them?

Answer 11

Mesenchymal swelling covered with surface ectoderm

Will form outer ear after migrating

Question 12

What germ layers form the auricular hillocks?

Answer 12

Mesenchyme
Surface ectoderm
NEURAL CREST COMPONENT

Question 13

What is the auricle innervated by?

Answer 13

Great auricular n.
CN v3- auriculotemporal branch
CN 7
CN 10- auricular branches

Question 14

What part of ear is first to develop?>

Answer 14

Inner ear

Question 15

What germ layer does the inner ear form from?

Answer 15

Surface ectoderm

Question 16

When does the inner ear begin to develop?

Answer 16

4th week

Question 17

How does the inner ear develop?

Answer 17

Surface ectoderm thickens and form the otic placode
Otic placode invaginate and forms otic pit
Otic pit rounds up and give us the otic vesicle
Otic vesicle migrates into the head and into petrous portion of the temporal bone

Makes the primordium of membranous labyrinth

Question 18

What is the embryological origin of the membranous labyrinth?

Answer 18

Surface ectoderm

Question 19

What makes up the membranous labyrinth?

Answer 19

Utricle (dorsal)
Saccule (ventral)
Hair cells

Question 20

What composes the utricle of the membranous labyrinth?

Answer 20

Endolymphatic duct and sac
Semicircular ducts and ampullae
Macula of utricle

Question 21

What composes the saccule of the membranous labyrinth?

Answer 21

Cochlear duct
Ducts reunions
Macula of saccule
Organ of corti

Question 22

Where are ducts of the inner ear found?

Answer 22

In the membranous labyrinth

Question 23

What fills the membranous labyrinth?

Answer 23

Endolymph

Question 24

What produces endolymph? What stores it?

What is endolymph?

Answer 24

Stria vascularis

Similar ion content to intracellular fluid with high K and protein but low Na

Endolymphatic sac stores endolymph

Question 25

What is the embryological origin of the bony labyrinth?

Answer 25

Mesenchyme (condensed)

Question 26

What is contained in the vacuoles of the bony labyrinth?

Answer 26

Perilymphatic space (semicircular canals) Scalia vestibule Scalia tympani

Question 27

What does the bony labyrinth form? | What does this separate it from?

Answer 27

Canal; separates it from membranous labyrinth

Question 28

What is contained in the bony labyrinth

Answer 28

Perilymph

Question 29

What does the perilymphatic allow for passage of?

Answer 29

Unobstructed passage from subarachnoid space to the inner ear

Question 30

What is the perilymph similar to?

Answer 30

Similar in ion content to CSF High na, low k and protein

Question 31

Where can things in perilymph go?

Answer 31

Can eventually migrate out into subarachnoid space

Question 32

What happens if you get a chronic ear infection in the tympanic cavity?

Answer 32

Can travel via a perilymph duct to the subarachnoid space

Question 33

What does the vestibulocochlear n. Develop from?

Answer 33

Otic placode (surface ectoderm)

Question 34

What comprises the Vestibular ganglion?

Answer 34

Collection of cell bodies from all the vestibular bodies (macula and ampullae) Vestibular n.

Question 35

What comprises the spiral (cochlear) ganglion?

Answer 35

Collection of cell bodies all around the cochlea from sensory neurons Cochlear n.

Question 36

What innervates the inner ear?

Answer 36

Hair cells

Question 37

Where do you find hair cells?

Answer 37

In the membranous labyrinth Specifically Ampulla of utricle Macula of utricle Organ of corti from saccule

Question 38

What do all hair cells of the inner ear originate from embryonically? Can they regenerate?

Answer 38

Surface ectoderm No

Question 39

What do the hair cells in the ampullae detect?

Answer 39

Rotational acceleration

Question 40

What do hair cells in the macula detect?

Answer 40

Gravity | Linear acceleration

Question 41

What do hair cells in the organ of corti detect?

Answer 41

Sound vibration

Question 42

What does the external auditory meatus develop from?

Answer 42

Pharyngeal cleft 1 - ectoderm

Question 43

What does the tubotympanic recess develop from?

Answer 43

Pharyngeal pouch 1 - endoderm

Question 44

What does the tympanic membrane develop from?

Answer 44

Pharyngeal membrane 1 - ectoderm, endoderm, mesoderm

Question 45

What are the ossicles covered with?

Answer 45

Endodermal epithelium

Question 46

What is the origin of the tubotympanic recess/

Answer 46

From pharyngeal pouch 1 Mastoid antrum Tympanic cavity Pharyngotympanic tube Endoderm

Question 47

What is the origin, insertion, action and innervation of Tensor Tympani M. ?

Answer 47

O: PA 1 mesoderm I: handle of malleus A: prevents damage from loud sound N: CN V3

Question 48

What is the origin, insertion, action and innervation of Stapedius M.?

Answer 48

O: PA 2 mesoderm I: neck of stapes A: pulls stapes posteriorly and tilts base in oval window, prevents damage from loud sounds N: CN 7

Question 49

What is a meatus plug?

Answer 49

Proliferation of the surface ectoderm over the external Auditory meatus that will eventually undergo apoptosis in late fetus life (Some people still have meatus plug)

Question 50

What is congenital deafness? What can it result from?

Answer 50

Inner ear form independently form middle and external ears causing maldevelopment of sound conduction apparatus of middle and external ears From: - 1st pharyngeal arch syndrome - abnormalities of malleus and incus - congenital fixation of the stapes - infections

Question 51

What infections could cause congenital deafness? | During what time?

Answer 51

``` Rubella infection - wk 7-8 - causing defect of spiral organ Cytomegalovirus Toxoplasmosis Symphysis Zika virus ```

Question 52

What does cytomegalovirus cause?

Answer 52

Sensorineural hearing loss

Question 53

What does the rubella virus cause in the ear?

Answer 53

Sensorineural deafness

Question 54

What does taxoplasma gondii cause in the ear?

Answer 54

Hearing loss

Question 55

What does taxoplasma gondii cause in the ear?

Answer 55

Congenital deafness