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Head and Neck Anatomy > Lectures 25 & 26 Ear > Flashcards

Lectures 25 & 26 Ear Flashcards

1
Q

Functions of ear?

A

Hearing, balance

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2
Q

Location of ear

A

temporal bone (apart from cartilagenous auditory tube)

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3
Q

Components of the ear

A
  • External ear
  • Middle ear (tympanic cavity)
  • Inner ear - cochlea, vestibule, semicircular canals
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4
Q

External ear function?

A

Collection of mechanical sound vibrations

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5
Q

Middle ear (tympanic cavity) function?

A

Transmission, amplification

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6
Q

Inner ear function?

A

Sensation

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7
Q

Describe external acoustic meatus

A
  • 24mm long
  • lateral 1/3 cartilagenous, medial 2/3 bony
  • Ceruminous glands (wax, modified sweat glands), hair in cartilagenous part only
  • Medial & slightly slanted anteriorly
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8
Q

Describe the tympanic membrane

A
  • elliptical, lateral surface concave
  • Skin externally, mucosa internally
  • a thickened edge, the tympanic ring fits into tympanic groove in temporal bone
  • handle of malleus attached to inner surface
  • Pars flacida above handle of malleus, pars tensa below
  • bottom of handle of malleus is umbo-point maximum convexity if viewed from middle ear.
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9
Q

Anatomy of the external ear

A
  • Superior crus
  • Helix
  • Inferior crus
  • Concha
  • Tragus
  • Antihelix
  • Antitragus
  • Lobule
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10
Q

Relations of the middle ear/tympanic cavity

A
  • Lateral wall
  • Anterior (carotid) wall
  • Posterior wall
  • Roof
  • Floor
  • Medial wall
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11
Q

Describe anterior (Carotid) wall

A

Opening of auditory tube. Tensor tympani runs in a canal above auditory tube & bends to run along medial wall.

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12
Q

Facial nerve branches to form chorda tympani behind anterior wall

A

False, posterior wall

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13
Q

Facial nerve turns superiorly at aditus

A

False, it turns inferiorly.

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14
Q

Posterior wall has an opening called the ‘aditus’ into the mastoid antrum and from there into the interconnecting air filled cavities of the mastoid air cells.

A

True

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15
Q

Tegmun tympani is the thin bone separating middle ear from middle cranial fossa

A

True

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16
Q

Tegmun tympani is medial to arcuate eminence when viewed from the inside of the skull.

A

False, it is lateral to arcuate eminence

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17
Q

The cavity of the middle ear immediately beneath tegmun tympani is the epitympanic recess

A

True

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18
Q

On the floor of the middle ear, the thin bone covering jugular fossa/foramen - middle ear infection can be transmitted to external jugular leading to spread of infection & possible clotting of jugular blood.

A

False, it is the internal jugular

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19
Q

Medial wall is adjacent to the inner ear - bony except for oval window which is closed by base of stapes & for round window to oval window.

A

True

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20
Q

Other features of medial wall include?

A
  • promontory inferomedially which overlies cochlea
  • Elevation which represents the canal for facial nerve
  • Round & oval windows
  • Tensor tympani
  • elevation overlying lateral semicircular canal
  • Tympanic plexus - tympanic branch of glossopharyngeal & sympathetic from internal carotid plexus
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21
Q

Where does chorda tympani leave the facial nerve?

A

5mm above stylomastoid foramen

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22
Q

Chorda tympani arches upwards across ________ wall of middle ear, passes between ___________ & ______, across upper part of tympanic membrane, then into bone again & down to petrotympanic fissure.

A

Posterior, long crus of incus, handle of malleus

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23
Q

Outside the skull, chorda tympani passes down ________ surface of spine of sphenoid & then between ________ & _______.

A

Medial, deep surface of lateral pterygoid, inferior alveolar nerve

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24
Q

Chorda tympani joins lingual nerve at an acute angle usually deep to medial pterygoid

A

False, lateral pterygoid

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25
Q

How are ossicles connected ?

A

They’re connected by synovial joints.

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26
Q

Ossicles are also attached to the wall of the middle ear by ligaments

A

True

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27
Q

What are ossicles covered by?

A

Mucosa

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28
Q

Describe the malleus

A
  • head in the epitympanic recess (superior), handle attached to tympanic membrane (& crossed by chorda tympani)
  • lateral & anterior processes (for ligaments)
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29
Q

Describe the incus

A
  • body articulates with the head of malleus
  • Long crus articulates with head of stapes
  • Short crus posteriorly (ligamentous attachment)
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30
Q

Describe the stapes

A
  • base (foot of stirrup) attaches to oval window
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31
Q

Epitympanic recess is part of the middle ear cavity below the level of the top of the eardrum

A

False, they are ABOVE

32
Q

Epitympanic recess contains head of malleus & part of the body of the incus.

33
Q

What are the muscles of the ear

A

Stapedius & tensor tympani

34
Q

What is the stapedius innervated by?

A

Stapedial branch of the facial nerve

35
Q

Where does the muscular part of the stapedius lie in and where does the tendon emerge from and attach to?

A

Muscular part lies in canal in posterior wall, tendon emerges from pyramid & attaches to neck of stapes

36
Q

Where is the tensor tympani muscle located and where does the tendon go?

A
  • muscle is within a bony canal above cartilagenous auditory tube
  • Tendon makes a 90 degree turn as it emerges & runs across middle ear to handle of malleus
37
Q

What is the tensor tympani innervated by?

A

Medial pterygoid branch CN5/3

38
Q

What is the function of the stapedius & tensor tympani?

A
  • Usually work together in a reflex response to high intensity sounds. Muscles contract & this reduces vibrations of the ossicles & in turn reduces sound intensity before it reaches the inner ear.
  • Tensor tympani also pulls the tympanic membrane inward (via malleus) which also reduces sound intensity transmission
  • Also reduces intensity of sounds produced by chewing
39
Q

Where does auditory tube stretch from?

A

Middle ear to nasopharynx

40
Q

Auditory tube is _______ posteromedially i.e. adjacent to middle ear

41
Q

Auditory tube is _______ anteromedially i.e. adjacent to nasopharynx

A

Fibrocartilage

42
Q

How is the cartilagenous auditory tube identified on the bony skull?

A

Groove on the underside of the skull between petrous temporal & posterior greater wing of sphenoid (medial to spine of sphenoid). Groove should run to narrow opening.

43
Q

What are the cartilagenous & bony parts of the auditory tube lined with?

A

Respiratory epithelium

44
Q

What does the inner ear consist of?

A

Bony labyrinth in petrous temporal bone.

45
Q

What is bony labyrinth lined with?

A

Hard compact bone, which is continuous with the spongy bone of the petrous temporal.

46
Q

What is the bony labyrinth filled with?

47
Q

What does perilymph separate?

A

Bony labyrinth from membranous labyrinth.

48
Q

T/F all the chambers of the osseous labyrinth interconnect

49
Q

What is the membranous labyrinth?

A

It is a separate series of hollow epithelial lined chambers which include sensory tissue.

50
Q

What does membranous labyrinth contain?

51
Q

Where is bony labyrinth located?

A

Petrous temporal bone

52
Q

Cochlea is ______ to vestibule

53
Q

Describe the vestibule in the inner ear/bonylabyrinth

A

Oval & round windows in lateral wall

54
Q

How many turns is the cochlea?

A

2.5 turns around central bony modiolis with the apex of the cochlea directed laterally.

55
Q

Describe the first turn of the cochlea

A

First turn produces the promontary in wall of middle ear.

56
Q

What does modiolis contain?

A

Spiral ganglion & there are bony channels which transmits fibres from ganglion to sensory cells in the cochleal duct.

57
Q

Describe the semicircular canals

A

Three canals posterosuperior to vestibule which communicate at their bases. Posterior canal is parallel to edge of middle cranial fossa. Anterior/superior canal is at right angles to edge of middle cranial fossa & vertical. Lateral is horizontal

58
Q

Semicircular canals of either ear are mirror images

59
Q

Anterior/superior canal produces ________ in floor of middle cranial fossa.

A

Arcuate eminence

60
Q

Lateral causes a horizontal bulge on medial wall of mastoid antrum above canal for facial nerve

61
Q

What are the three interconnecting parts of membranous labyrinth

A

Cochleal duct, vestibule, semicircular ducts

62
Q

What does semicircular ducts contain?

A

Endolymph.

63
Q

What does each semicircular duct incorporate?

A

A dilated region or ampulla at the vestibular end with sensory structure - crista - head movement

64
Q

What is the sensory structure in semicircular duct?

A

Crista - for head movement

65
Q

What does the membranous part of the vestibule consist of?

A

Two connected sacs containing endolymph - utricle & saccule - each has a sensory region or macula - head position

66
Q

What is sensory region of utricle & saccule?

A

Macula for head position

67
Q

Cochleal duct is a blindly ending duct

68
Q

What are the extensions of the bony labyrinth?

A

Scala vestibuli (from vestibule) & scala tympani (to round window)

69
Q

Scala vestibuli and scala tympani are continuous with each other at the apex of the cochlea

70
Q

What does cochleal duct contain and incorporate?

A

Endolymph, sensory organ of Corti

71
Q

What does scala vestibuli & tympani contain?

A

Perilymph (vibrations in the perilymph transmit sound)

72
Q

Summarise the sensory regions?

A
  • Cochlea: organ of corti
  • Saccule & utricle: maculae
  • Semicircular canals: crista
73
Q

Where does the facial and vestibulocochlear nerve emerge from?

A

At inferior border of pons with nervus intermedius between (sensory & parasympathetic root of facial)

74
Q

Where do vestibulocochlear nerves pass through?

A

Canal & the two components separate at the external end of the internal acoustic canal

75
Q

Where does vestibular nerve go to?

A

Sensory vestibular ganglion in outer part of inner ear

76
Q

Where does cochlear nerve go to?

A

Sensory spiral ganglion in modiolis

Head and Neck Anatomy (13 decks)

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