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ESA 3- Head & neck > 7. Anatomy of the ear > Flashcards

7. Anatomy of the ear Flashcards

1
Q

which skull bone (specific parts) contains structures of ear

A

temporal bone: - tympanic part - surrounds EAM opening - petrous part - contains middle and inner ear - mastoid process - mastoid antrum extends through this to communicate with air cells

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2
Q

what are the functions of the external ear and name its 3 components

A

Collects, transmits and focuses sound waves onto tympanic membrane: 1- auricle 2- external auditory meatus 3- lateral surface of tympanic membrane

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3
Q

what is earwax

A

discarded epithelial cells + cerumen (protection and aids desquamation) secreted by the epithelium lining the cartilaginous part of the EAM

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4
Q

label

A
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5
Q

which important structures does the middle ear (typanic cavity) contain

A

the ossicles - 3 bones connected via synovial joints that transmit vibrations from the tympanic membrane to the inner ear cochlea (i.e. from air mediul to fluid medium)

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6
Q

name the 3 ossicles and describe their arrangement

A
  1. handle of MALLEUS attached to tympanic membrane…
  2. while its body articulates with that of INCUS…
  3. which also articulates with STAPES…
  4. which articulates with bony labyrinth of cochlea at OVAL WINDOW
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7
Q

why can facial n palsy lead to hyperacusis

A
  • STAPEDIUS and TENSOR TYMPANI (innervated by branches of facial n) act to tamper movement of ossicles
  • provide protective acoustic reflex: contract if potentially excessive vibration due to loud noise
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8
Q

explain the importance of the Eustachian (pharyngotympanic) tube

A

Connects the tympanic cavity to the nasopharynx (ie external environment):

1- allows equilibration of pressure within cavity with that of atmosphere, as middle ear mucous membrane is continuously reabsorbing air, causing negative pressure

2- ventilation

3- drainage

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9
Q

explain why middle ear pathology can cause clinical signs of a facial n lesion

A

runs in close proximity to middle ear:

1- facial n runs for most part in own bony canal - facial canal - which separates it from middle ear cavity by v thin bony partition

2- chorda tympani branch actually runs through middle ear cavity on inner surface of tympanic membrane

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10
Q

label

A
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11
Q

label

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12
Q

what separates the bony labyrinth from the membranous labyrinth

A

perilymph

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13
Q

describe which components of the inner ear allow sound perception

A
  • COCHLEAR DUCT houses the SPIRAL ORGAN OF CORTI where receptors of the auditory appararus - STEREOCILIA - are found
  • Stereocilia respond to fluid motion within duct endolymph (generated by stapes tapping on oval window) to generate APs that are propagated down cochlear part of vestibulochochlear n
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14
Q

describe which components of the inner ear allow position and balance perception

A

VESTIBULAR APPARATUS consisting of:

  1. VESTIBULE surrounding UTRICLE and SACULE
  2. 3 SEMICIRCULAR DUCTS and CANALS

Utricle, sacule and semicircular ducts also contain endolymph of stereocilia which responds to:

  • rotational acceleration and static pull of gravity (utricle and saccule)
  • rotational acceleration in 3 different places (semi-circular ducts)

Bending of stereocilia generates APs relayed via vestibular part of vestibulocochlear n

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15
Q

describe the innervation of the auricle

A
  • mandibular n. of CN V (auriculotemporal n) - anterior to EAM
  • cervical spinal n. C2 (greater auricular n) - posterior ear, helix, antihelix and lobule
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16
Q

describe the innervation of the EAM and external tympanic membrane

A
  • mandibular n. of CN V (auriculotemporal n) - external surface
  • some innervayion via auricular branch of vagus n (eg concha of auricle)
17
Q

describe the innervation of the internal tympanic membrane and middle ear cavity

A

glossopharyngeal n

18
Q

explain why URT infections or pathology further down pharynx/larynx can cause referred ear pain

A
  • URT infections (pharyngitits/tonsillitis) can cause referred pain in ear due to shared sensory innervation of oropharynx with that of middle ear - GLOSSOPHARYNGEAL N
  • pathology of lower pharynx/larynx can cause referred ear pain due to shared sensory innervation of laryngopharynx and larynx with external ear - VAGUS N
19
Q

describe the process of hearing

A
  1. auricle and EAM focus and funnel sound towards typanic membrane which vibrates accordingly…
  2. vibration of ossicles, with stapes beating on oval window, provokes vibration/movement in cochlear endolymph…
  3. sensed by stereocilia in spiral organ of Corti of cochlear duct…
  4. mov of stereocilia trigger APs in cochlear part of CN VIII…
  5. primary auditory cortex in temporal lobe processes information.

ESA 3- Head & neck (22 decks)

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