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KJLee > 1: Anatomy of the ear > Flashcards

1: Anatomy of the ear Flashcards

1
Q

What are the four parts of the temporal bone

A

Squamous
Mastoid
Petrous
Tympanic

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2
Q

What muscles attach to the mastoid process?

A 
Sternocleidomastoid
Splenious capitus
Longissimus capitus
Digastric
Anterior, superior, and posterior digastric
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3
Q

How much of the EAC is cartilaginous vs osseous?

A

1/3 cartilaginous (lateral)

2/3 osseous (medial)

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4
Q

How does the skin covering the cartilaginous vs osseous portions of the EAC differ?

A

Cartilaginous: has sebacious and cerumenous glands and hair follicles
Osseous: skin is tight over the periosteum

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5
Q

What bones form the osseous portion of the EAC?

A

Tympanic part of the temporal bone: anterior portion, floor, and part of the posterior portion
Squamosa: roof and the remainder of the posterior portion

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6
Q

What three ligaments attach the auricle to the head?

A

Anterior: zygoma to helix and tragus
Superior: EAC to the spine of the helix
Posterior: mastoid to concha

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7
Q

What space is found posterior and superior to the EAC and approximates the position of the antrum medially?

A

Macewen’s triangle

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8
Q

Macewen’s triangle is bound at the meatus by:

A

Spine of Henle

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9
Q

What area is bounded by the bony labyrinth, the sigmoid sinus, and the superior petrosal sinus?

A

Trautmann’s triangle

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10
Q

What is the clinical significance of Trautmann’s triangle?

A

Posterior transpetrosal approaches

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11
Q

What is Citelli’s angle? What is it the angle between?

A

Sinodural angle: between the sigmoid sinus and the middle fossa dural plate

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12
Q

What is the name of the thin plate of bone that constitutes the lateral wall of the epitympanum (part of the squamosa)

A

Scutum

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13
Q

What is Huguier’s canal?

A

Transmits the chorda tympani out of the temporal bone anteroirly

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14
Q

What is the porus acousticus?

A

The mouth of the internal auditory canal, divided horizontally by the crista falciformis

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15
Q

What are the three general parts of the inner ear?

A

Pars superior: vestibular labyrinth
Pars inferior: cochlea and saccule
Endolymphatic sac and duct

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16
Q

What is Koerner’s septum?

A

Anatomic boundary in the temporal bone formed by the petrosquamous suture between the petrous and the squamousal portions of the mastoid air cells
Located at the anatomic level of the antrum

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17
Q

What proportion of the population has a pneumatized petrous portion of the temporal bone?

A

1/3

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18
Q

What is the scala communis?

A

Where the scala tympani joins the scala vestibuli

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19
Q

What is the name of the apex of the cochlea where the scala tympani and vestibuli join

A

Helicotrema

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20
Q

What is the name of the bony channel connecting the scala tympani of the basal turn with the subarachnoid space of the posterior cranial cavity

A

Cochlear aquaduct

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21
Q

What nerves form the tympanic plexus of the middle ear?

A

CN V3 -> auriculotemporal nerve
CN IX -> Jacobson’s nerve
CN X -> Auricular nerve

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22
Q

What are the three layers of the TM?

A

Squamous epithelium
Fibrous layer (radiating and circular)
Mucosal layer

23
Q

What is the average size of the TM?

Average vibrating surface?

A

70-80 mm2

55 mm2

24
Q

What are the anatomical parts of the malleus?

A 
Head
Neck
Manubrium 
Anterior process
Lateral process (or short)
Facet for articulation with the stapes
25
Q

What are the anatomic components of the incus?

A

Body
Short process
Long process (lenticular)

26
Q

What are the anatomic components of the stapes?

A

Anterior crus
Posterior crus
Footplate

27
Q

What does the stapedial tendon connect?

A

Apex of the pyramidal process to the posterior surface of the neck of the stapes

28
Q

What types of joints are the malleal:incudal, incudo:stapedial, and stapedial:labyrinth

A

Diarthroidal
Diarthroidal
Syndesmotic

29
Q

The oval window sits in the ____ plane

The round window sits in the ____ plane

A

Sagittal

Axial

30
Q

The tensor tympani inserts from the _____ process onto the medial surface of the upper end of the manubrium

A

Cochleariform

31
Q

What is the function of the tensor tympani?

A

Pulls the TM medially, tensing it
Draws the malleus medial and forward
Raises resonance frequency and attenuates low frequencies

32
Q

What does the stapedius muscle attach to?

A

Posterior neck of the stapes (sometimes the posterior crux)

Pyramidal process

33
Q

How long is the eustachian tube at birth? Adulthood?

A

15-17 mm

35 mm

34
Q

What happens to the configuration of the eustachian tube from birth to adulthood?

A

Starts horizontal

Inclines to 45% downsloping from the tympanic orifice, which ends up 15 mm above the pharyngeal orifice

35
Q

What is the composition of the eustachian tube?

A

Anteromedial 2/3 cartilaginous

Posterolateral 1/3 bony

36
Q

The cartilaginous portion of the eustachian tube is lined with pseudostratified columnar ciliated epithelium until it nears the tympanic orifice and switches to–

A

ciliated cuboidal epithlium

37
Q

What two muscles work in synergy to open the eustachian tube? What is their respective innervation?

A 
Tensor palati (3rd division of CN V)
Levator veli palatini (CN X)
38
Q

Why are cleft palate children expected to have eustachian tube dysfunction for a time?

A

Initially only the tensor palati works in children, as the levator veli palatini is too far away
In cleft palate children, there is poor tensor palatini function and they have poor eustachian tube function until the levator veli palatini starts functioning

39
Q

Why are there more eustachian tube problems when a plane is descending?

A

More difficult to expel air from the middle ear then to get it in

40
Q

What is the critical pressure difference that can cause the eustachian tube to ‘lock’, prohibiting the tensor palatini from opening it?

A

90 mmHg

41
Q

What is the pressure differential at which there is risk for TM rupture?

A

100 mmHg

42
Q

How much pressure does a Valsalva produce?

A

20-40 mmHg

43
Q

What is the name of the lymphoid tissue in the eustachian tubes?

A

Tonsils of Gerlach

44
Q

During what week of gestation does the auricle begin to form?
What is the embryonic origin of the auricle?

A

6th week

Mesoderm of the 1st and 2nd arches

45
Q

What are the hillocks of His?

A

Six hillocks that arise from mesoderm, first three from the 1st arch and second three from the 2nd arch–form the auricle

46
Q

What is the anatomic component that is formed by each of the hillocks of His?

A

First: tragus
Second: helical crus
Third: helix

Fourth: antihelix
Fifth: antitriagus
Sixth: lobule and lower helix

47
Q

At what week of gestation do the hillocks of His fuse? When is the adult ear formed?

A

12th week

20th week

48
Q

When does the ear reach adult size?

A

9 yo

49
Q

What does improper fusion of the first and second branchial arches result in?

A

Epithelium lined preauricular sinus tract

50
Q

What percent of preauricular cysts are bilateral?

A

20%

51
Q

What syndrome is characterized by:

  • Outward downslanted eyes
  • Notched lower lid
  • Short mandible
  • Bony meatal atresia
  • Malformed incus and malleus
  • Fishmouth
A

Treacher collins (first arch syndrome)

52
Q

What is another name for treacher collins?

A

Mandibulofacial dysostosis

53
Q

How frequently is the tympanic portion of the facial nerve dehiscent?

A

20-30%

54
Q

What is Hyrtl’s fissure? What is it’s clinical significance?

A

Present in infants, extends from the hypotympanum (anterior and inferior to the round window) to the subarachnoid space
Route of direct extension of infection from the middle ear to the subarachnoid space

KJLee (22 decks)

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