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Neuro Exam 3: Anatomy > Anatomy and Embryo: Ear > Flashcards

Anatomy and Embryo: Ear Flashcards

1
Q

auricle

A

collects airwaves and funnels them into external acoustic meatus
- made of elastic cartilages, lobules and depressions

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2
Q

blood supply to auricle?

A

post auricular a/v

superficial temporal a/v

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3
Q

innervation to auricle?

A
  • Great auricular and lesser occipital nn (C2,3)
  • auriculotemporal n (V3), facial n, vagus n.
  • lymph drains to mastoid, parotid lymph nodes and to deep cervical lymph nodes
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4
Q

external acoustic meatus

A

canal traveling through tympanic portion of temporal bone to tympanic membrane

  • lined by stratified squamous
  • lateral 1/3 cartilaginous, medial 2/3 bony
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5
Q

blood supply to external acoustic meatus

A

post. auricular a/v

superficial temporal a/v

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6
Q

innervation to external acoustic meatus

A

auriculotemporal n (V3)
Vagus n.
all lymph drains to deep cervical nodes

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7
Q

otitis externa

A

inflammation of external ear

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8
Q

tympanic membrane

A
  • converts sound waves into vibrations of middle ear ossicles.
  • fibroelastic membrane, connected to malleus.
  • covered externally by epidermis and internally by mucus membrane
  • membrane is anterior and inferior
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9
Q

blood supply to tymp. membrane?

A

external surface: deep auricular branch of maxillary a.

internal surface: anterior tymp. branch of maxillary a.

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10
Q

innervation to tymp membrane?

A

external surface: auriculotemporal n (V3), vagus n.

internal surface: glossopharyngeal n. (endodermally derived)

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11
Q

how does auricle develop?

A

derived from cartilage of 1st/2nd pharyngeal arches

* defects often associated with most chromosomal syndromes *

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12
Q

how does external aud. meatus develop?

A

first pharyngeal cleft

- meatul plug forms, if does not degenerate by 7th month, will cause deafness and congenital hearing loss

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13
Q

tympanic membrane development?

A

external ectoderm= ectoderm of first pharyngeal cleft

middle CT= mesoderm of first pharyngeal arch

internal epithelium = endoderm of first pharyngeal arch

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14
Q

fn of middle ear

A
  • contains tympanic cavity, a mucous lined space w/in petrous portion of temporal bone and auditory ossicles.
  • fn = transfer of sound waves from gas to liquid medium (from external to internal ear).
  • amplifies sound waves in the process via bony ossicles
  • protective response to loud sounds (tensor tympani, stapedius mm.)
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15
Q

what forms boundaries of tympanic cavity?

A

roof: tegmen tympani (seperates epitympanic recess from middle cranial fossa)
floor: temporal bone (seperates from IJV)

lateral wall: tymp membrane

medial wall: promontory, oval window, round window

post wall: temporal bone

ant wall: temporal bone

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16
Q

what are portions of medial wall?

A
  1. promontory: mound of bone created by cochlea
  2. oval window(fenestrae vestibule): opens to vestibule of inner ear: contacted by stapes; transmits motion of stapes to fluid of internal ear.
  3. round window (fenestra cochlea): opens to scala tympani; covered with thin membrane: acts as a pressure release valve for fluids of internal ear
17
Q

what does posterior wall contain?

A
  • seperates middle ear from mastoid air cells
  • aditus ad antrum = entrance to mastoid antrum
  • facial canal = passage of facial n.
18
Q

mastoiditis

A
  • infections of nasopharynx can spread to auditory tube, then into middle ear.
  • middle ear infections, can sometimes spread to mastoid air cells
  • from mastoid air cells the infections can spread superior into the middle cranial fossa
19
Q

what is contained in anterior wall

A
  • receives opening from pharyngotympanic tube and semi-canal

- tensor tympani passes through here (works to dampen vibrations)

20
Q

pharyngotympanic tube

A

“auditory tube”

  • located in anterior wall
  • mucous membrane connects middle ear and nasopharynx
  • fn: balances pressure on external and internal sides of tympanic membrane

** tensor veli palatine: mm. attaches to membranous portion of auditory tube and can open the membranous tube via CN V3 (allowing for equalization of inner ear)

21
Q

what are the auditory ossicles?

A
  1. malleus (contacts TM)
  2. incus (middle)
  3. stapes (contacts oval window)- vibration moves fluid within cochlear duct
  • work on an amplification system, all are united by synovial joints

*** osteosclerosis = synovial joints become thick = conductive hearing loss

22
Q

stapedius

A 
= mm. of the inner ear 
O: post wall of tymp. cavity
I: stapes
fn: dampens mvmts of ossicles (contracts reflexively in response to loud noises)
n: facial n - SVE
23
Q

tensor tympani

A

O: cartilagenous part of pharyngotymp. tube
I: malleus
fn: dampens mvmt of ossicles (contracts when chewing and speaking)
n: trigeminal n (V3) SVE

24
Q

paralysis of middle ear mm?

A

can cause hyperacusis = excessive hearing acuteness = due to loss of dampening mm.

25
Q

blood supply to Tm?

A
  • inferior tymp (ascending pharyngeal)
  • ant tymp (maxillary)
  • post tymp (stylomastoid)
  • superior tymp (middle meningeal a.)
26
Q

how does CN IX provide the ear?

A

glossopharyngeal n.
-supplies GVA and GVE-P to middle ear

  • tympanic branch (GVA, GVE-P) enters middle ear via tympanic canaliculus; forms tympanic plexus.
  • tympanic plexus provides GVA sensory and GVE-P innervation for middle ear.
  • lesser petrosal n. reforms from tymp. plexus and exits midle ear via hiatus for lesser petrosal n (GVE-P)–> PS to parotid gland
27
Q

how does CN VII supply ear?

A

supplies motor innervation to stapedius (SVE)

  • enters internal acoustic meatus, courses along roof of inner ear toward middle ear
  • within middle ear CN VII travels within facial canal on posterior wall
  • chorda tympani is given off right before CN VII exitsmiddle ear at stylomastoid m=foramen, corda tympani passes b/w incus and malleus and exits the middle ear via petrotympanic fissure

** corda tympani: provides SVA to ant 2/3 of tongue and GVE-P to submandibular and sublingual glands

28
Q

otitis media?

A

inflamation of middle ear; often due to spread of infection from pharynx via pharyngotympanic tube

29
Q

what are three branches of facial n. in middle ear?

A
  1. greater petrosal n (GVE-P to pterygopalatine ganglion)
  2. n. to stapedius
  3. corda tympani (SVA and GVE-P to glands)
30
Q

how is middle ear derived? TQ

A

tympanic cavity and auditory tube = first pharyngeal pouch

malleus, incus, tensor tympani: first pharyngeal arch

stapes, stapedius = second pharyngeal arch

** congenital fixation of stapes can cause deafness due to problem with 2nd arch **

31
Q

membranous labyrinth

A

this is where sound is processed
- membranous ducts contained within bony labyrinth that are filled with endolymph
(bony labyrinth filled w/ perilymph)
- cochlear duct: processes sounds : hair cells are housed in spiral organ

32
Q

Vestibulocochlear n

A

CN VIII

  • exits brainstem at pontomedullary jn.
  • passes through internal acoustic meatus to enter inner ear
  • vestibular portion innervates semicircular ducts, utricle, saccule, carrying proprioceptive info
  • cochlear portion innervates coochlear duct and carries info about sound
33
Q

how is inner ear derived?

A

membranous labyrinth: develops from otic placode (ectoderm)

bony labyrinth (vestibule, semicircular canals, cochlea), from surrounding mesenchyme of otic placode

Neuro Exam 3: Anatomy (12 decks)

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