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ENT: Anatomy > The Ear > Flashcards

The Ear Flashcards

1
Q

what is the external ear comprised of?

A

cartilaginous pinna (auricle) and external acoustic meatus (ear canal)

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2
Q

what marks the medial end of the external acoustic meatus?

A

tympanic membrane

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3
Q

what is the pinna formed of?

A

elastic cartilage attached to the temporal bone encased in skin

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4
Q

where does the cartilage of the pinna gain nutrients from?

A

the skin

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5
Q

what part of the external acoustic meatus is cartilage?

A

lateral 1/3rd

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6
Q

what gland produces earwax?

A

ceruminous glands

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7
Q

what instrument is used to examine the external acoustic meatus and tympanic membrane

A

otoscope

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8
Q

why is the ear pulled posterosuperiorly when examining an adult’s ear using an otoscope?

A

the external acoustic meatus is curved

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9
Q

sensory innervation to the external pinna

A

C2, 3 spinal nerves
CNV3 (superior EAM and most of tympanic membrane)
CNX (inferior EAM and a bit of tympanic membrane)
CNVII

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10
Q

borders of the middle ear

A

tympanic cavity from the tympanic membrane to the oval window of the inner ear

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11
Q

what bones are located in the middle ear?

A

auditory ossicles (malleus, incus and stapes)

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12
Q

role of the ossicles

A

convey vibration from the tympanic membrane to the apparatus of the inner ear

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13
Q

what connects the ossicles?

A

synovial joints

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14
Q

how are the ossicles attached to the wall of the tympanic cavity?

A 
ligaments
mucosal folds (which carry vessels and nerves)
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15
Q

two muscles in the tympanic cavity

A

tensor tympani

stapedius

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16
Q

describe the tensor tympani

A

inserts onto the malleus from eustachian tube, innervated by CNV3
it dampens sound by reducing vibrations from the tympanic membrane (consider oral cavity)

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17
Q

describe stapedius

A

inserts into stapes running from the pyramidal eminence and innervated by CNVII. It reduces vibrations of stapes on the oval window

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18
Q

which reflex do both tensor tympani and stapedius have a role in?

A

acoustic reflex (protection from shouting)

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19
Q

what bone is the tympanic cavity located in?

A

petrous portion of the temporal bone

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20
Q

two parts of the tympanic cavity

A

tympanic cavity proper

epitympanic recess

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21
Q

sensory innervation of the mucosa lining the middle ear

A

CNIX (glossopharyngeal)

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22
Q

what does the posterior tympanic cavity contain?

A

mastoid aditus (opens into the air cells of the mastoid)

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23
Q

risk of the mastoid aditus

A

risk of mastoiditis, osteomyelitis and meningitis

also used as surgical access to the tympanic cavity

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24
Q

describe the roof of the tympanic cavity

A

tegmen tympani is a thin plate of bone separating the middle cranial fossa

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25
Q

what is the floor of the tympanic cavity closely related to?

A

internal jugular vein

26
Q

what does the medial wall of the tympanic cavity contain?

A

oval window
round window
promontory
facial canal

27
Q

role of the round window

A

dissipates force from the cochlear

28
Q

what is the promontory

A

bump from the first turn of the cochlear, tympanic plexus lies over this and is derived from the glossopharyngeal nerve

29
Q

what supplies the parotid gland

A

lesser petrosal nerve (branch of CNIX)

30
Q

what is the anterior wall of the tympanic cavity closely related to?

A

carotid canal containing the internal carotid artery
eustachian tube
chorda tympani

31
Q

what does the eustachian tube connect?

A

middle ear and nasopharynx (posterior to inferior nasal concha)

32
Q

passage of the chorda tympani in the tympanic cavity

A

between malleus and incus towards the infratemporal fossa

33
Q

what is the eustachian tube made of?

A

posterior third is formed by bone while the remainder is cartilaginous (typically collapsed but becomes patent during muscular contraction)

34
Q

role of the eustachian tube

A

equalise air pressure between the middle ear and nasopharynx

35
Q

what is the mucosa of the middle ear continuous with?

A

nasal cavity

36
Q

sensory innervation of the mucosa of the middle ear, eustachian tube, nasopharynx, oropharynx and palatine tonsils?

A

CNIX

consider referred otalgia

37
Q

role of the inner ear

A

reception of sound and maintenance of balance

38
Q

location of the inner ear in terms of the bone

A

deep within the petrous portion of the temporal bone

39
Q

what does the inner ear consist of?

A

bony labyrinth (fluid-filled network in the otic capsule) and membranous labyrinth (communicating ducts and sacs)

40
Q

role of the cochlear

A

hearing

41
Q

role of the SSC, utricle and saccule

A

balance

42
Q

what is the densest part of the temporal bone?

A

otic capsule

43
Q

three parts to the bony labyrinth

A
  1. cochlear
  2. vestibule
  3. semi-circular canals
44
Q

describe the cochlear

A

shell-shaped spiral cavity encircling a bony core (modiolus)

also have the round window)

45
Q

describe the vestibule

A

small oval-shaped chamber containing the utricle and saccule (vestibular organs/otolioth organs) also contains the round window

46
Q

what converts mechanical stimuli to neural stimuli in the ear?

A

mechanoreceptors called hair cells

47
Q

where are the hair cells located?

A

basilar membrane of the macules of the utricle and saccule and ampullae of the SSC

48
Q

how do APs reach the CNS from hair cells?

A

travel via the vestibular nerve part of the vestibulocochlear nerve (CNVIII)

49
Q

what are the three fluid-filled channels of the cochlear

A
  1. scala vestibuli
  2. scala tympani
  3. scala media
50
Q

what is the site called where the scala vestibuli and tympani are continuous with each other?

A

helicotrema

51
Q

what does the modiolus contain?

A

canals for conveying blood vessels and distributing branches of the cochlear nerve

52
Q

what muscles open the eustachian tube to equalise air pressure?

A

palatine muscles

53
Q

how can pressure be relieved

A

valsalva manoeuvres

54
Q

define barotrauma

A

trauma due to unequalised air pressure

55
Q

what does the tympanic membrane do if atmospheric pressure is more than the tympanic cavity?

A

pushes inwards

56
Q

what does the tympanic membrane do if the atmospheric pressure is less than the pressure in the tympanic cavity?

A

membrane pushes out

57
Q

why is otitis media more common in children?

A

under-developed immune system

shorter distance between middle ear and eustachian tube

58
Q

how does bacteria/viruses spread from the pharynx/tonsils to the middle ear?

A

eustachian tube

59
Q

steps to show how sound is produced into electrical stimuli

A
  1. sound waves make the tympanic membrane vibrate
  2. vibrations are transmitted through ossicles
  3. footplate of stapes vibrates in oval window
  4. vibrations of stapes creates pressure waves in perilymph
  5. hair cells are moved and APs stimulated and conveyed to the brain via the cochlear nerve
  6. pressure waves descend and become vibration being dampened at the round window
60
Q

what is the vestibular apparatus responsible for?

A

balance and perception of head movement

61
Q

what do the semi-circular canals detect

A

angular movement change

  • urticle horizontal
  • saccule vertical
62
Q

what structures pass through the internal acoustic meatus?

A

facial nerve CNVII
vestibulocochlear nerve CNVIII
labyrinthine artery (+ veins)-circle of willis

ENT: Anatomy (14 decks)

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