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Neuro > Ear Development > Flashcards

Ear Development Flashcards

1
Q

When does the ear begin to develop?

A

week 4 (goes to week 20)

*if a problem does occur, it’ll probably be b/t week 4-8

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2
Q

What is in the external Ear?

A

– Consists of auricle (pinna), external acoustic meatus, external layer of tympanic membrane

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3
Q

What is in the middle Ear?

A

– Consists of three ossicles, internal layer of tympanic membrane, and middle ear cavity

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4
Q

What is coming from inner Ear?

A

– Consists of vestibulocochlear organ

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5
Q

Where do the external and middle ear come from? inner ear?

A
  1. Pharyngeal arches
  2. develops independently

*can have problems with E/M and I is fine

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6
Q

What arches does the external ear come from? Innervation?

A
  1. pharyngeal arches 1 +2

2. CNV3 (auriculotemporal), CN X (auricular branches), CN VII, Great Auricular (C2 + C3)

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7
Q

What covers the external ear?

A

Covered with ectoderm that becomes the skin, and underneath made of auricular hillocks
mesenchymal swellings covered with ECTODERM (NC component)

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8
Q

What are auricular hillocks?

A

mesenchymal swellings (NC cells) covered by surface ectoderm; NC cells migrate to pull external ectoderm which gives rise to different aspects of the external ear

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9
Q

What part of the external ear came from the first arch?

A

half of ear attached to body

rest comes from arch 2

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10
Q

What nerve innervates arch 1? 2?

A
  1. CN 5

2. CN 7

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11
Q

How do Auricular Skin tags form?

A

problem with migration of surface ectoderm, and if cartilage is there, then abnormal migration of NC cells too

*always will have skin

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12
Q

How do we get Anotia?

A

NC and Auricular hillocks do not form/migrate

*NC cells of arch 1 + 2 did not migrate properly

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13
Q

What are pharyngeal arches made of?

A

Ectoderm, mesoderm, endoderm, + NC components

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14
Q

What causes Microtia?

A

NC cells form arches 1 + 2 migrate abnormally

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15
Q

How does the external auditory meatus form?

A

the 1st pharyngeal cleft (ectoderm) invaginate in

*it fills in with cells to form the meatal plug, and at 6 months they go through apoptosis to open up the EAM

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16
Q

What is the inner ear developed? what is it derived from?

A 
week 4 (first to develop)
surface ectoderm
17
Q

What structures to help with inner ear development form in week 4?

A
  1. Otic placode - forms near hindbrain, surface ectoderm; invaginate to from otic pit
  2. Otic Pit - connects to itself, and migrates in to form otic vesicle
  3. Otic vesicle - own little pouch, gives rise to membranous labyrinth
18
Q

What does the membranous labyrinth come from/form?

A

comes from otic vesicle, and forms utricle (dorsal) and saccule (ventral)

19
Q

What is the utricle? Where does it come from? What controls its development?

A
  1. Utricle + Semicircular Canal
  2. Membranous Labyrinth
  3. Dlx5 + Dlx6
20
Q

What is the saccule? Where does it come from? What controls its development?

A
  1. Cochlear Duct, Ductus reunions, Macula of saccule, organ of corti
  2. Membranous Labyrinth
  3. Pax6 (cochlear duct is dependent on Pax 2)
21
Q

How do the semicircular canal/ducts form?

A

endo lymphatic duct/sac–>developing semi –> functional semi

*lateral canal dependent on Otx1

22
Q

What is the function of the ducts reunions?

A

connects saccule (from saccule) to the utricle (from utricle)

23
Q

Where do we find hair cells? What do they do?

A
  1. Ampullae - acceleration
  2. Macula - gravity
  3. Organ of cortical - sound vibration
  • come from SURFACE ECTODERM
  • *when they bend, it leads to innervation of the inner ear
  • **do not regrow (if lost, you go deaf)
24
Q

What is the innervation of the inner ear?

A

CN 8 - goes to hair cells

comes from two sources:

  1. vestibular ganglion
  2. spiral (cochlear) ganglion
  • both have contributions from surface ectoderm via otic placode
  • Vestibular ganglion also has neural crest contribution
25
Q

Where does perilymph come from? What is it made of?

A
  1. From perilymphatic duct or filtration of blood in perilymphatic space
  2. Similar content to CSF

*b/t duct and bone

26
Q

Where does endolymph come from? what is it made of?

A
  1. Stria vascularis
  2. similar to ICF
  • endolymphatic sac stores it
  • found within duct
27
Q

If we get an infection in the middle ear, and it eroded through the round/oval window, what happens?

A

offers a direct route to the subarachnoid space and you get meningitis

28
Q

What is the bony labyrinth? function?

A
  1. condensation of mesenchyme (mesoderm)
  2. protects membranous labyrinth

*vacuoles around cochlear duct called scala tympani + vestibuli

29
Q

How does the bony labyrinth form?

A

mesoderm around cochlear duct –> as it grows you get vacuoles which develop sacral vestibuli and scala tympani –> ends with bony around the ST/SV/scala media and cochlea

*week 5-8

30
Q

What surrounds the spiral ganglion?

A

bony labyrinth

*send its nerve fibers into basal membrane to be discharged to pick up impulses for sound

31
Q

Of the 1st pharyngeal cleft, what does the ectoderm form? endoderm?

A
  1. External Auditory Meatus

2. Tubotympnaic recess (and eventually tympanic cavity)

32
Q

What is the tympanic membrane derived from?

A

ecto, meso, and endo

  • external surface (N: Auriclotemporal + Vagus)
  • *blood supply to TM
  • **internal surface (N: CN 9)
33
Q

What are the ear bones made of?

A

NC

Malleus and include are form 1st arch NC

Stapes is from 2nd arch NC

*covered with endodermal epithelium from 1st pharyngeal pouch

34
Q

Where does the Tensor Tympani come from?

A

Pharyngeal arch 1 -mesoderm

-Innervated by CN 5

35
Q

Where does anything innervated by CN 5 come from?

A

arch 1

36
Q

Where does stapedius come from?

A

Pharyngeal arch 2 - mesoderm

-Innervated by CN 7

37
Q

Why do you sound different than you hear your voice as?

A

Stapedius + Tympani tense to ensure your voice doesn’t damage your ears

38
Q

Congenital Deafness Causes

A
  1. Most times genetic
  2. Maldevelopment of sound conduction apparatus of middle and external ears (arch 1 + 2)
    a. First arch syndrome
    b. Abnormalities of malleus and incus (1st arch)
    c. Congenital fixation of stapes
  3. Neurosensory sensory structures of inner ear
  4. Rubella infection during week 7-8 can cause defects of spiral organ and deafness

Neuro (10 decks)

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