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RA 2 > Applied Anatomy of the Ear > Flashcards

Applied Anatomy of the Ear Flashcards

1
Q

List the 3 divisions of the ear.

A

1 - Outer ear.

2 - Middle ear.

3 - Inner ear.

*This lecture focuses on the outer and middle ear.

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2
Q

Which bone forms the bony layer of the outer ear?

A

The tympanic part of the temporal bone.

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3
Q

What is the pinna of the ear?

A

The visible part of the outer ear.

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4
Q

List the functions of the outer, middle and inner ear.

A
  • The outer ear collects sound from the auditory space and funnels it towards the middle ear.
  • The middle ear transduces sound energy into movements of joints of the ossicle chain.
  • The inner ear transduces movements of the ossicle chain into electrical impulses of hearing.
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5
Q

What is the isthmus of the ear?

A

The thinnest part of the auditory canal near to the tympanic membrane.

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6
Q

List the embryological structures that give rise to the outer and middle ear.

Are these structures of ectodermal, mesodermal or endodermal origin?

A
  • The outer ear is derived from the first pharyngeal cleft, which is of ectodermal origin.
  • The middle ear is derived from the first pharyngeal pouch, which is of endodermal origin.
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7
Q

List the embryological structures from which the mucosa lining the pharynx and auditory tube is derived.

A

1 - First pharyngeal pouch.

2 - Second pharyngeal pouch.

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8
Q

Which embryological structure gives rise to the inner ear?

Where is this structure located during development?

A

The otic placode, which is located behind the second pharyngeal arch.

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9
Q

Describe the sensory innervation of the outer ear.

A
  • The upper 1/3 of the outer ear is innervated by the auriculotemporal branch of CN V3.
  • The middle 1/3 of the outer ear is innervated by the lesser occipital nerve, which is a spinal nerve of roots C2 - C3.
  • The lower 1/3 of the outer ear is innervated by the greater auricular nerve, which is a spinal nerve of roots C2 - C3.
  • The central area of the outer ear (and continuing this, the ear canal) is innervated by the auricular branch of the vagus nerve.
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10
Q

Describe the sensory innervation to the middle ear.

A

1 - The auriculotemporal branch of CN V3.

2 - The tympanic branch of CN IX.

3 - The auricular branch of CN X.

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11
Q

List the embryological structures that give rise to the muscles of the middle ear.

A
  • Tensor tympani is derived from the first pharyngeal arch.

- Stapedius is derived from the second pharyngeal arch.

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12
Q

Which nerve innervates muscles derived from the first pharyngeal arch?

A

The mandibular branches of CN V.

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13
Q

Which nerve innervates muscles derived from the second pharyngeal arch?

A

The facial nerve.

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14
Q

What is perichondrium?

What is its function.

A
  • The connective tissue that covers cartilage.

- It supplies the cartilage with nutrients.

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15
Q

What is cauliflower ear?

A

Necrosis of the cartilage of the ear resulting from separation of the perichondrium from the cartilage due to a haematoma.

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16
Q

What proportion of the external auditory canal is cartilaginous?

What proportion of the external auditory canal is formed by the temporal bone?

A
  • The outer 1/3 is formed of elastic cartilage.

- The inner 2/3 is formed of the tympanic plate of the temporal bone.

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17
Q

How do the innermost regions of the external auditory canal differ in appearance from the outermost regions?

A

The number of hair cells decreases towards the innermost regions.

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18
Q

What is the ear-cough reflex?

Which afferent nerve is involved?

A
  • Stimulation of the external auditory canal (by touch) excites the auricular branch of the vagus nerve.
  • This initiates a reflex, causing a cough.
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19
Q

List the layers of the tympanic membrane?

A

1 - Outer plate.

2 - Middle plate.

3 - Inner plate.

20
Q

Give an example of an indication that the tympanic membrane is attached to the ear.

A

It is concave laterally.

21
Q

Of which structure is the outer plate of the tympanic membrane a continuation?

A

The outer plate of the tympanic membrane is a continuation of the skin of the external auditory canal.

22
Q

Of which structure is the inner plate of the tympanic membrane a continuation?

A

The inner plate of the tympanic membrane is a continuation of the skin of the lining of the pharynx.

23
Q

List the cell types that comprise the lateral, middle and medial areas of the tympanic membrane.

A
  • Laterally, the tympanic membrane is composed of keratinised stratified squamous cells.
  • In the middle, the tympanic membrane is composed of a fibrous layer.
  • Medially, the tympanic membrane is composed of respiratory epithelium (a ciliated columnar epithelium).
24
Q

Describe the sensory innervation of the tympanic membrane.

A
  • The internal surface is innervated by CN IX.

- The external surface is supplied by the auriculotemporal branch of CN V3, and sometimes by the vagus nerve.

25
Q

List the surfaces of the middle ear.

A

1 - Lateral wall, formed by the inner plate of the tympanic membrane.

2 - Medial wall, formed by the outer plate of the oval window.

3 - Roof, formed by the tegmen tympanum.

4 - Floor, formed by the jugular wall.

5 - Posterior wall, formed by the mastoid wall.

6 - Anterior wall, formed by the carotid wall.

26
Q

List the bones of the middle ear.

A

1 - Malleus.

2 - Incus.

3 - Stapes.

27
Q

What is the chorda tympani?

What other structure does it innervate?

Why might this be relevant clinically?

A
  • A sensory branch of CN VII located in the middle ear.
  • It also innervates the tongue for taste sensation.
  • This means that damage to the ear can result in changes in taste.
28
Q

What is the name of the canal connecting the middle ear to the mastoid antrum?

What is the mastoid antrum?

A
  • The ‘aditus to mastoid antrum’.

- The mastoid antrum contains air cells that act as a reservoir of air.

29
Q

Which epithelium lines the middle ear?

A

Ciliated pseudostratified columnar epithelium similar to respiratory epithelium.

30
Q

What is the epitympanic recess?

A

A hollow located on the superior roof of the middle ear containing the aditus to mastoid antrum.

31
Q

Through which structure does the middle ear communicate with the nasopharynx?

A

The eustachian tube.

32
Q

What proportion of the eustachian tube is cartilaginous?

What proportion of the eustachian tube is formed by the temporal bone?

A
  • The posterolateral 1/3 is bony.

- The anteromedial 2/3 is cartilaginous.

33
Q

Which muscles open the walls of the eustachian tube?

Which section of the eustachian tube is opened by these muscles?

A
  • Palate levator and tensor veli palatini open the walls of the eustachian tube.
  • They open the anteromedial 2/3 (cartilaginous part) of the eustachian tube.
34
Q

What are the primary and secondary functions of the eustachian tube?

A
  • The primary function is to equalise the pressure in the middle ear with the atmospheric pressure.
  • The secondary function is the drain the mucus secretions of the middle ear.
35
Q

What might result from eustachian tube dysfunction?

A
  • Failure to drain mucus secretions of the middle ear, leading to congestion.
  • The epithelia of the middle ear begin to remove air from the secretions, producing negative pressure in the middle ear.
  • This is known as glue ear.
36
Q

List 3 contributing factors to otitis media Infection of the middle ear).

A

1 - Eustachian tube dysfunction.

2 - Infection of the middle ear.

3 - Nasal inflammation.

37
Q

Why are children more prone to developing otitis media than adults?

A

Because the eustachian tube in children is more horizontal.

38
Q

Why might otitis media cause the tympanic membrane to bulge into the external auditory canal?

A

Because otitis media might cause an inflammatory reaction, producing fluids in the middle ear.

39
Q

What is the most common pathogen that causes otitis media?

A

Streptococcus pneumoniae.

40
Q

What is otitis media with effusion?

A
  • Otitis media where the middle ear become secretory.

- Secretions of the middle ear accumulate with products of inflammation.

41
Q

Give an example of a complication of otitis media.

A
  • Mastoiditis.

- This occurs when the infection spreads to the mastoid antrum.

42
Q

List 3 areas other than the mastoid antrum into which infections causing otitis media can spread.

Through which openings can this happen?

A

1 - The middle cranial fossa via the temporal bone.

2 - Posterior cranial fossa via the mastoid antrum.

3 - The sigmoid venous sinus via mastoid air cells.

43
Q

What happens in osteosclerosis of the ear?

A

The stapes fuses to the oval window, resulting in dampened movements of the ossicles.

44
Q

What is the oval window?

A

A membrane-covered opening that leads from the middle ear to the inner ear.

45
Q

Which bone forms the middle and inner ear?

A

The petrous part of the temporal bone.

46
Q

List the parts of the temporal bone.

A

1 - Squamous.

2 - Mastoid.

3 - Petrous.

4 - Tympanic.

RA 2 (7 decks)

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