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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
How are ossicles connected ?
They're connected by synovial joints.
26
Ossicles are also attached to the wall of the middle ear by ligaments
True
27
What are ossicles covered by?
Mucosa
28
Describe the malleus
- head in the epitympanic recess (superior), handle attached to tympanic membrane (& crossed by chorda tympani) - lateral & anterior processes (for ligaments)
29
Describe the incus
- body articulates with the head of malleus - Long crus articulates with head of stapes - Short crus posteriorly (ligamentous attachment)
30
Describe the stapes
- base (foot of stirrup) attaches to oval window
31
Epitympanic recess is part of the middle ear cavity below the level of the top of the eardrum
False, they are ABOVE
32
Epitympanic recess contains head of malleus & part of the body of the incus.
True
33
What are the muscles of the ear
Stapedius & tensor tympani
34
What is the stapedius innervated by?
Stapedial branch of the facial nerve
35
Where does the muscular part of the stapedius lie in and where does the tendon emerge from and attach to?
Muscular part lies in canal in posterior wall, tendon emerges from pyramid & attaches to neck of stapes
36
Where is the tensor tympani muscle located and where does the tendon go?
- 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
What is the tensor tympani innervated by?
Medial pterygoid branch CN5/3
38
What is the function of the stapedius & tensor tympani?
- 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
Where does auditory tube stretch from?
Middle ear to nasopharynx
40
Auditory tube is _______ posteromedially i.e. adjacent to middle ear
Bony
41
Auditory tube is _______ anteromedially i.e. adjacent to nasopharynx
Fibrocartilage
42
How is the cartilagenous auditory tube identified on the bony skull?
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
What are the cartilagenous & bony parts of the auditory tube lined with?
Respiratory epithelium
44
What does the inner ear consist of?
Bony labyrinth in petrous temporal bone.
45
What is bony labyrinth lined with?
Hard compact bone, which is continuous with the spongy bone of the petrous temporal.
46
What is the bony labyrinth filled with?
Perilymph
47
What does perilymph separate?
Bony labyrinth from membranous labyrinth.
48
T/F all the chambers of the osseous labyrinth interconnect
True
49
What is the membranous labyrinth?
It is a separate series of hollow epithelial lined chambers which include sensory tissue.
50
What does membranous labyrinth contain?
Endolymph
51
Where is bony labyrinth located?
Petrous temporal bone
52
Cochlea is ______ to vestibule
anterior
53
Describe the vestibule in the inner ear/bonylabyrinth
Oval & round windows in lateral wall
54
How many turns is the cochlea?
2.5 turns around central bony modiolis with the apex of the cochlea directed laterally.
55
Describe the first turn of the cochlea
First turn produces the promontary in wall of middle ear.
56
What does modiolis contain?
Spiral ganglion & there are bony channels which transmits fibres from ganglion to sensory cells in the cochleal duct.
57
Describe the semicircular canals
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
Semicircular canals of either ear are mirror images
True
59
Anterior/superior canal produces ________ in floor of middle cranial fossa.
Arcuate eminence
60
Lateral causes a horizontal bulge on medial wall of mastoid antrum above canal for facial nerve
True
61
What are the three interconnecting parts of membranous labyrinth
Cochleal duct, vestibule, semicircular ducts
62
What does semicircular ducts contain?
Endolymph.
63
What does each semicircular duct incorporate?
A dilated region or ampulla at the vestibular end with sensory structure - crista - head movement
64
What is the sensory structure in semicircular duct?
Crista - for head movement
65
What does the membranous part of the vestibule consist of?
Two connected sacs containing endolymph - utricle & saccule - each has a sensory region or macula - head position
66
What is sensory region of utricle & saccule?
Macula for head position
67
Cochleal duct is a blindly ending duct
True
68
What are the extensions of the bony labyrinth?
Scala vestibuli (from vestibule) & scala tympani (to round window)
69
Scala vestibuli and scala tympani are continuous with each other at the apex of the cochlea
True
70
What does cochleal duct contain and incorporate?
Endolymph, sensory organ of Corti
71
What does scala vestibuli & tympani contain?
Perilymph (vibrations in the perilymph transmit sound)
72
Summarise the sensory regions?
- Cochlea: organ of corti - Saccule & utricle: maculae - Semicircular canals: crista
73
Where does the facial and vestibulocochlear nerve emerge from?
At inferior border of pons with nervus intermedius between (sensory & parasympathetic root of facial)
74
Where do vestibulocochlear nerves pass through?
Canal & the two components separate at the external end of the internal acoustic canal
75
Where does vestibular nerve go to?
Sensory vestibular ganglion in outer part of inner ear
76
Where does cochlear nerve go to?
Sensory spiral ganglion in modiolis

Head and Neck Anatomy (13 decks)

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