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Neuro > Ear Development > Flashcards

Ear Development Flashcards

1
Q

What makes up the external ear?

A

Auricle
EAM
External layer of the tympanic membrane

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2
Q

What makes up the middle ear?

A

3 ossicles
Internal layer of tympanic membrane
Middle ear cavity

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3
Q

What makes up the internal ear?

A

Vestibulocochlear organ

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4
Q

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

A

Weeks 4-8

But still out to wk. 20

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5
Q

What is the auricle formed from?

A

PA 1 and 2

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6
Q

What is the external acoustic meatus formed from?

A

PA 1 groove -ectoderm

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7
Q

What is the tympanic membrane formed from?

A

PA 1 membrane (Mesenchyme, ectoderm and endoderm)

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8
Q

What is the origin of the malleus?

A

PA 1

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9
Q

What is the origin of the incus?

A

PA 1

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10
Q

What is the origin of the Stapes?

A

PA 2

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11
Q

How do the auricular hillocks develop?

What is the fate of them?

A

Mesenchymal swelling covered with surface ectoderm

Will form outer ear after migrating

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12
Q

What germ layers form the auricular hillocks?

A

Mesenchyme
Surface ectoderm
NEURAL CREST COMPONENT

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13
Q

What is the auricle innervated by?

A

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

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14
Q

What part of ear is first to develop?>

A

Inner ear

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15
Q

What germ layer does the inner ear form from?

A

Surface ectoderm

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16
Q

When does the inner ear begin to develop?

A

4th week

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17
Q

How does the inner ear develop?

A

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

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18
Q

What is the embryological origin of the membranous labyrinth?

A

Surface ectoderm

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19
Q

What makes up the membranous labyrinth?

A

Utricle (dorsal)
Saccule (ventral)
Hair cells

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20
Q

What composes the utricle of the membranous labyrinth?

A

Endolymphatic duct and sac
Semicircular ducts and ampullae
Macula of utricle

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21
Q

What composes the saccule of the membranous labyrinth?

A

Cochlear duct
Ducts reunions
Macula of saccule
Organ of corti

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22
Q

Where are ducts of the inner ear found?

A

In the membranous labyrinth

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23
Q

What fills the membranous labyrinth?

24
Q

What produces endolymph? What stores it?

What is endolymph?

A

Stria vascularis

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

Endolymphatic sac stores endolymph

25
Q

What is the embryological origin of the bony labyrinth?

A

Mesenchyme (condensed)

26
Q

What is contained in the vacuoles of the bony labyrinth?

A

Perilymphatic space (semicircular canals)
Scalia vestibule
Scalia tympani

27
Q

What does the bony labyrinth form?

What does this separate it from?

A

Canal; separates it from membranous labyrinth

28
Q

What is contained in the bony labyrinth

29
Q

What does the perilymphatic allow for passage of?

A

Unobstructed passage from subarachnoid space to the inner ear

30
Q

What is the perilymph similar to?

A

Similar in ion content to CSF

High na, low k and protein

31
Q

Where can things in perilymph go?

A

Can eventually migrate out into subarachnoid space

32
Q

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

A

Can travel via a perilymph duct to the subarachnoid space

33
Q

What does the vestibulocochlear n. Develop from?

A

Otic placode (surface ectoderm)

34
Q

What comprises the Vestibular ganglion?

A

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

35
Q

What comprises the spiral (cochlear) ganglion?

A

Collection of cell bodies all around the cochlea from sensory neurons

Cochlear n.

36
Q

What innervates the inner ear?

A

Hair cells

37
Q

Where do you find hair cells?

A

In the membranous labyrinth

Specifically

Ampulla of utricle
Macula of utricle
Organ of corti from saccule

38
Q

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

Can they regenerate?

A

Surface ectoderm

No

39
Q

What do the hair cells in the ampullae detect?

A

Rotational acceleration

40
Q

What do hair cells in the macula detect?

A

Gravity

Linear acceleration

41
Q

What do hair cells in the organ of corti detect?

A

Sound vibration

42
Q

What does the external auditory meatus develop from?

A

Pharyngeal cleft 1 - ectoderm

43
Q

What does the tubotympanic recess develop from?

A

Pharyngeal pouch 1 - endoderm

44
Q

What does the tympanic membrane develop from?

A

Pharyngeal membrane 1 - ectoderm, endoderm, mesoderm

45
Q

What are the ossicles covered with?

A

Endodermal epithelium

46
Q

What is the origin of the tubotympanic recess/

A

From pharyngeal pouch 1
Mastoid antrum
Tympanic cavity
Pharyngotympanic tube

Endoderm

47
Q

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

A

O: PA 1 mesoderm

I: handle of malleus

A: prevents damage from loud sound

N: CN V3

48
Q

What is the origin, insertion, action and innervation of

Stapedius M.?

A

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

49
Q

What is a meatus plug?

A

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)

50
Q

What is congenital deafness?

What can it result from?

A

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
51
Q

What infections could cause congenital deafness?

During what time?

A 
Rubella infection - wk 7-8 - causing defect of spiral organ 
Cytomegalovirus 
Toxoplasmosis
Symphysis
Zika virus
52
Q

What does cytomegalovirus cause?

A

Sensorineural hearing loss

53
Q

What does the rubella virus cause in the ear?

A

Sensorineural deafness

54
Q

What does taxoplasma gondii cause in the ear?

A

Hearing loss

55
Q

What does taxoplasma gondii cause in the ear?

A

Congenital deafness

Neuro (18 decks)

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