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Neuro Exam 1 > Ear Development > Flashcards

Ear Development Flashcards

1
Q
  • During what week do the ears begin developing?
  • What is the critical period for ear development?
  • Ears develop thru WEEK _
A
  • 4
  • 4-8
  • 20
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2
Q
  • Parts of the external ear
A
  • Auricle (pinna)
  • External acoustic meatus
  • External layer of tympanic membrane
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3
Q
  • What are the parts of the middle ear?
A
  • Ossicles (malleus, incus, stapes)
  • Internal layer of tympanic membrane
  • Middle ear cavity
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4
Q
  • What are the parts of the internal ear?
A

Vestibulocochlear organ

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5
Q
  • The auricle of the external ear is derived from _
A
  • 1st and 2nd pharyngeal arches
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6
Q
  • Auricular hillocks are _ swellings covered with _
  • The neural crest components of the auricular hillocks migrates and pulls surface ectoderm to form parts of the external ear
A
  • Mesenchymal, ectoderm
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7
Q
  • Innervation of the external ear
A
  • CN V3: Auriculotemporal
  • CN X: Auricular branches
  • CN VII: Facial N
  • Great Auricular N (sensation)
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8
Q
  • How do these form?
A
  • Abnormal migration of surface ectoderm
  • If cartilage is also present in skin tags, there was also abnormal migration of NCCs
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9
Q
  • What condition is shown in the following image?
  • What embryological mechanism explains this?
A
  • Anotia
  • Auricular cells and NCCs did not migrate or form
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10
Q
  • What is shown in the following image?
  • What embryological mechanism can account for this?
A
  • Microtia
  • NCCs from 1st and 2nd pharyngeal arch migrated abnormally
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11
Q
  • The _ (made from ectoderm) invaginates and forms the external auditory meatus
  • It fills with cells and around 6 months of age undergoes apoptosis
A
  • 1st pharyngeal cleft
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12
Q
  • What is shown in the following image?
A
  • Meatal plug
  • Surface ectodermal cells that helped form the external auditory meatus did not undergo apoptosis @ 6 mo
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13
Q
  • _ is the first part of the ear to develop
  • What germ layer is it derived from?
  • At what week does it begin to form?
A
  • Inner ear
  • Ectoderm
  • 4th week
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14
Q
  • During the 4th week the _ invaginates to form the otic pit
  • The otic pit then forms the _, which gives rise to the primordium of the membranous labyrinth
A
  • Otic placode
  • Otic vesicle
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15
Q
  • What are the two parts of the membranous labyrinth?
A
  • Utricle (dorsal)
  • Saccule (ventral)

Ball sacks are in the front (ventral)

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16
Q
  • Development of the utricle is dependent on what genes?
  • What are the components of the utricle?
A
  • DLX 5 and DLX 6
  • Endolymphatic duct and sac
  • Semicircular ducts and ampullae (DLX 5 and DLX 6)
    • Lateral canal (OTX1)
  • Macula of utricle
17
Q
  • Development of the saccule is dependent on what genes?
  • What are its components?
A
  • PAX 6 (Cochlear duct)
  • Ductus reunions-connects vestibular cochlea to vestibular apparatus
  • Macula of saccule, organ of Corti
18
Q
  • Innervation of the inner ear
A
  • Hair cells (from surface ectoderm of otic vesicle)
    • Ampullae-acceleration
    • Macula-gravity
    • Organ of Corti-Sound vibration
  • Cranial nerve VIII (vestibulocochlear n.)
    • Vestibulocochlear ganglion (Surface ectoderm adn NCC component)
    • Spiral (cochlear) ganglion
19
Q
  • Perilymph
    • _ is usually patent and enables free passage from the subarachnoid space into the inner ear
    • Similar in ion concentration to _
A
  • Perilymphatic duct
  • CSF (High Na+, Low K+ and Protein)
20
Q
  • Endolymph
    • _ produces endolymph
    • Similar in ion concentration to _
    • _ stores it
A
  • Stria vascularis
  • Intracellular fluid (High K+ and protein, low Na+)
  • Endolymphatic sac
21
Q
  • _ duct connects with the subarachnoid space
  • Why is this bad?
A
  • Perilymphatic
  • Inner ear infections can invade the subarachnoid space and lead to meningitis
22
Q
  • Function of the bony labyrinth
  • Vacuoles form
A
  • Protects membranous labyrinth
    • Perilymphatic space (semicircular ducts)
    • Scala vestibuli
    • Scala tympani
23
Q
  • The first pharyngeal cleft comes from what embryological germ layer?
  • What structure does it form?
A
  • Ectoderm
  • External auditory meatus
24
Q
  • The 1st pharyngeal pouch comes from what embryological germ layer?
  • What structure does it form?
A
  • Endoderm
  • Tubotympanic recess (and eventually tympanic cavity)
25
Q
  • The tympanic membrane is derived from what embryological germ layer
A
  • Ectoderm (External surface-V3 Trigeminal, Parts of Vagus N.)
  • Mesoder
  • Endoderm (Internal surface-glossopharyngeal n.)
26
Q
  • The malleus and incus form from what embryological germ layer
A
  • 1st arch (Neural Crest Cells)
27
Q
  • The stapes forms from what embryological germ layer?
A
  • 2nd arch (Neural Crest Cells)
28
Q
  • The ossicles are covered with _ epithelium
A
  • Endodermal (that came from the first pharyngeal pouch)
29
Q
  • Tensor tympani
    • Comes from which pharyngeal arch
    • What innervates it
A
  • Action prevents damage from loud sounds
  • 1st pharyngeal arch
  • Innervated by CN V (Anything from CN V comes from 1st pharyngeal arch)
30
Q
  • Stapedius m
    • Function
    • What pharyngeal arch is it derived from
    • Innervation
A
  • Pulls stapes posteriorly and tilts its base in the oval window and prevents damage from loud sounds
  • 2nd pharyngeal arch
  • Innervated by CN VII
31
Q
  • Congenital deafness
A
  • Inner ear forms independently from middle and external ears
  • Causes
    • Genetic
    • Maldevelopment of sound-conduction apparatus of middle and external ears
      • First arch syndrome
      • Abnormalities of malleus and incus (1st pharyngeal arch)
      • Congenital fixation of the stapes (can’t move or transmit sounds)
  • Neurosensory structures of inner ear
  • Rubella infection during 7-8 week causes defects of spiral organ and deafness

Neuro Exam 1 (14 decks)

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