Lecture 15: Ear Development Flashcards

1
Q

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

A

Weeks 4-8

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2
Q

When does development of the ear occur?

A

Week 4-20

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3
Q

What is found in the external, middle, and inner ear?

A

External Ear

  • Auricle
  • External Acoustic Meatus
  • External Layer of Tympanic Membrane

Middle Ear

  • Auditory Ossicles (3)
  • Internal Layer of Tympanic Membrane
  • Middle Ear Cavity

Inner Ear

  • Vestibulocochlear Organ
  • Develops separately from external and internal ear
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4
Q

The medial part of the external ear came from what pharyngeal arch?

A

1st Pharyngeal Arch

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5
Q

The lateral part of the external ear came from what pharyngeal arch?

A

2nd Pharyngeal Arch

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6
Q

The mesenchymal swellings located within the pharyngeal arches are known as what?

A

Auricular Hillocks

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7
Q

What are the cells that migrate and pull the surface ectoderm around to form the external ear?

A

Neural crest cells of the auricular hillocks

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8
Q

Auricular skin tags that may contain cartilage are a result of what?

A

Abnormal migration of surface ectoderm and neural crest cells

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9
Q

Abnormal or absent migration of the NCCs and auricular hillocks can result in what disorders?

A

Anotia

Microtia

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10
Q

What embryonic layer does the meatal plug arise from?

A

Surface ectoderm

1st Pharyngeal Cleft

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11
Q

What embryonic layer forms the tubotympanic recess?

A

Endoderm: 1st Pharyngeal Pouch

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12
Q

What embryonic layer does the inner ear arise from?

A

Surface ectoderm

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13
Q

How does the inner ear form from surface ectoderm?

A
  1. Otic Placode thickens
  2. Invaginates to form Otic Pit
  3. Becomes Otic Vesicle that migrates to the head
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14
Q

What embryonic structure gives rise to the membranous labyrinth?

A

Otic vesicle

Also Surface Ectoderm

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15
Q

What does the dorsal side of the otocyst give rise to?

A

Utricle

  1. Endolymphatic duct and sac
  2. Semicircular ducts and ampullae
  3. Macula of utricle
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16
Q

What does the ventral side of the otocyst give rise to?

A

Saccule

  1. Cochlear duct
  2. Ductus reuniens
  3. Maccula of saccule
  4. Organ of Corti
17
Q

What structure connects the cochlea to the vestibular apparatus?

A

Ductus reuniens

18
Q

What is the embryonic layer that gives rise to the hair cells of the inner ear?

A

Surface ectoderm

19
Q

Where are hair cells located in the inner ear?

What does the respective hair cells sense?

A
  • Ampullae of Semicircular Canals
    • Rotational Acceleration
  • Macula of utricle and saccule
    • Linear Acceleration
  • Organ of Corti (cochlea)
    • Soun Vibration
20
Q

What nerve is responsible for innervation to the inner ear?

Where did this nerve come from?

A

CN VIII: Vestibulocochlear Nerve

Otic Placode

21
Q

What are the embryonic contributions to the vestibular ganglion?

What cell bodies contribute to this?

A

Neural crest cells and surface ectoderm

Cell bodies from macula and ampullae

22
Q

What is the embryonic contribution to the spiral (cochlear ganglion)?

A

Surface ectoderm

23
Q

What structures does the perilymphatic duct provide passage between?

A

Subarachnoid space to inner ear

24
Q

What is the ion content of perilymph?

A

High Na+

Low K+ and Protein

(Similar to CSF)

25
Q

What is the ion content of endolymph?

A

High K+ and Protien

Low Na+

(Similar to ICF)

26
Q

What produces endolymph?

A

Stria Vascularis

27
Q

What embryonic layer does the bony labyrinth arise from?

A

Mesoderm

Condensation of Mesenchyme

28
Q

What are the vacuoles of the bony labyrinth?

A

Scala Vestibuli

Scala Tympani

Semicircular Ducts (Perilymphatic Space)

29
Q

What suspends the cochlear duct within the bony labyrinth and attaches it to the wall?

A

Spiral Ligament

30
Q

What bones of the middle ear arise from the 1st pharyngeal arch?

What is their embryonic origin?

A

Malleus and Incus

Neural Crest Cells

31
Q

The stapes bone arises from what arch?

What is the embryonic origin?

A

2nd Pharyngeal Arch

Neural crest cells

32
Q

What embryonic layer does the epithelium covering the ossicles arise from?

A

Endoderm

33
Q

What are the embryonic layers making up the tympanic membrane?

A

Arive from 1st Pharyngeal Membrane

  • Ectoderm: from 1st Pharyngeal Cleft
  • Mesoderm
  • Endoderm: from 1st Pharyngeal Pouch
34
Q

What pharyngeal arch does the Tensor Tympani Muslce arise from?

What embryonic layer?

What innervates this muscle?

A

1st Pharyngeal arch

Mesoderm

CN V3

35
Q

What pharyngeal arch does the Stapedius Muslce arise from?

What embryonic layer?

What nerve innervates it?

A

2nd Pharyngeal Arch

Mesoderm

CN VII

36
Q

What part of the fetal ear is affected if there is a maternal Rubella infection?

A

Inner ear: Spiral Organ/Organ of Corti defects

37
Q

What is the leading cause of congenital sensorineural hearing losss?

A

Cytomegalovirus