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Year 2 Term 2 C&M > C: Ear > Flashcards

C: Ear Flashcards

1
Q

List the structures through which soundwaves pass before reaching the auditory receptors?

A

1) External auditory canal
2) Tympanic membrane
3) Maleus
4) Incus
5) Stapes
6) Vestibule
7) Cochlea
8) Organ of conti

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2
Q

What is the function of the tympanic membrane?

A

Convert soundwaves into mechanical vibrations

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3
Q

What are the ossicles?

A

Small bones found in the ear

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4
Q

What is the function of the ossicles?

A

Amplify mechanical vibrations

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5
Q

What is the oval window?

A

Membrane covered window leading from middle ear to inner ear

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6
Q

What is the function of the oval window?

A

Point of attachment for base of stapes, ends the chain of bones which transfer the vibrations initiated by tympanic membrane to cochlea of inner ear

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7
Q

What is the function of the round window?

A

Pressure valve which moves out when the oval window moves in

enables improved fluid flow:
allows fluid flow that transfers vibrations to hairs of cochlea

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8
Q

What are the primary and secondary functions of the auditory/Eustachian tube?

A

Primary - maintain middle ear at atmospheric pressure (equalisation of pressure)
Secondary - drain any accumulated secretions, infections or debris from middle ear space

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9
Q

What is the external auditory canal lined by?

A

Skin which produces ear wax

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10
Q

What is ear wax made up of? 7

A

1) Keratinocytes
2) Anti-microbial peptides
3) Alcohols
4) Squalene
5) Cholesterol
6) Triglycerides
7) Lysozyme

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11
Q

How does ear wax travel along the ear canal?

A

Moved outwards by motions from chewing and other jaw movements

As the skin of the canal grows from inside out - migrating skin cells

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12
Q

What lies at the end of the external auditory canal?

A

Tympanic membrane

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13
Q

From what is the name chorda tympani (branch of facial nerve) derived?

A

From its route in the middle ear - it is located behind the tympanic membrane

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14
Q

What is the function of the chorda tympani? 2

A

1) Taste anterior 2/3 of tongue

2) PS to submandibular and sublingual salivary glands

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15
Q

What forms the lateral wall of the air filled chamber known as the middle ear?

A

The tympanic membrane

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16
Q

What are the main contents of the middle ear?

A

The ossicles - maleus, incus and stapes

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17
Q

What epithelium is the middle ear lined by, what are the possible clinical consequences of this?

A

Lined by respiratory epithelium

Liable to infection in URT disease, it is connected anteroinferiorly to the nasopharynx

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18
Q

Via what is the middle ear connected to the nasopharynx?

A

The eustachian tube

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19
Q

What is the mastoid antrum?

A

Collection of mastoid air cells, mucous membrane is continuous with that of the middle ear

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20
Q

Through what opening is the middle ear connected posteriorly to the mastoid air cells?

A

Aditus to mastoid antrum

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21
Q

Why are meningitis, brain abscess and sigmoid sinus thrombosis potential complications of middle ear infection?

A

Mucous membrane lining the mastoid air cells is continuous with the mucous membrane lining the middle ear.

Infections can easily spread into mastoid area:

osteomyelitis spreading into the middle cranial fossa.

Brain abscesses, meningitis and inflammatory cell presence can also lead to venous thrombosis

22
Q

Why is facial nerve damage a potential complication of middle ear infection?

A

Facial canal transverses the middle ear - if the walls of this become eroded by infection - risk of damage to the nerve

23
Q

Tensor tympani muscle is located partly in middle ear, what is the nerve supply and function?

A

Nerve - branch from mandibular nerve (V3)
Pulls the handles of malleus medially

Tensing of the tympanic membrane reduces the force of vibrations in response to loud noises

24
Q

Stapedius muscle is located partly in the middle ear, what is the nerve supply and function?

A

Nerve to stapedius muscle (CN7)

prevents excessive movement/ oscillation of stapes bone, controlling the amplitude of sound waves

25
Q

The inner ear/bony labyrinth is a cavity lying within which bone?

A

The petrous temporal bone

26
Q

What fluid fills the inner ear cavity?

A

Perilymph

27
Q

What is the membranous labyrinth?

A

Epithelial sac lying within the inner ear

28
Q

What fluid fills the membranous labyrinth?

A

Endolymph

29
Q

What are the 3 kinds of sensory receptors within the walls of the membranous labyrinth?

A

1) Maculae - vestibular receptors
2) Christae ampullaris - vestibular receptors
3) Spiral organ (organ of conti) - auditory receptors

30
Q

In which region of the membranous labyrinth are the maculae located?

A

Saccule and utricle

31
Q

The maculae are concerned with what type of sensory information?

A

Providing sensory info about the static position of the head in space - aiding the maintenance of balance

32
Q

In which regions of the membranous labyrinth are the christae ampullaris located?

A

The ampulla of the 3 semi circular ducts which lie within the semicircular canals of the bony cavity of the petrous temoral bone

33
Q

The christae ampullaris are concerned with what type of sensory information?

A

Sensory info about changes in the direction and rate of movement of the head

34
Q

Give 3 structural similarities between the maculae and the christae ampullaris?

A

1) Have hair cells of the same morphological type (type 1 and 2)
2) Hair cells of both have numerous stereocilia and a single kinocilium
3) The stereocilia and kinocilia are embedded in a ridge of gelatinous glycoprotein in both

35
Q

In which nerve do the axons of first order sensory neurons associated with these receptors travel to the brainstem?

A

Vestibular part of CN8 - vestibulocochlear nerve

36
Q

Injury to the peripheral vestibular system can lead to which 2 conditions?

A

1) Nystagmus

2) Vertigo

37
Q

What is meant by nystagmus?

A

Rapid involuntary movements of the eyes

38
Q

What is meant by vertigo?

A

Sensation of motion in which the individuals surroundings appear to spin

39
Q

What is the cochlear duct?

A

The part of the membranous labyrinth lying within the snail shaped bony cochlea.

It is filled with endolymph.

The cochlear duct starts at the saccule and ends blindly at the apex of the cochlea.

40
Q

What is the organ of conti?

A

Specialised region in the wall of the cochlea duct

41
Q

The bony cochlea and its enclosed cochlear duct spiral how many times around the central axis of bone?

A

2.5

42
Q

What does the central axis of bone contain?

A

The spiral ganglion - made up of cell bodies of first order auditory neurons

43
Q

Fluid movement within the middle ear causes which part of the organ of conti to vibrate?

A

Basilar membrane

44
Q

What 3 compartments can the cochlear duct be split into, which 2 membranes separate them?

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

Scala vestibuli seperated from the scala media (containing the organ of conti) by the vestibular membrane

Scala media seperated from scala tympani by the basilar membrane

45
Q

How does vibration of the basilar membrane differ with differing frequency?

A

Each point on the basilar membrane (from the base of the membranous cochlear to the apex) vibrates maximally in response to sound of a particular frequency

46
Q

How does vibration of the basilar membrane lead to action potentials?

A

1) Basilar membrane vibration causes the hairs (stereocilia) to be deformed against the overlying, gelatinous tectorial membrane.
2) This deformity causes depolarisation/hyperpolarisation of the sensory hair cells and generates action potentials in the sensory nerve fibres synapsing at the base of the cells

47
Q

Which region of the basilar membrane vibrates maximally in response to sounds of high frequency?

A

Basilar membrane towards base of cochlear

48
Q

Which region of basilar membrane vibrates maximally in response to sounds of low frequency?

A

Basilar membrane further along spiral towards apex

49
Q

Where are the cell bodies of sensory fibres which contact the hear cells?

A

Spiral ganglion

50
Q

Which cranial nerve do the first order sensory fibres join?

A

Auditory part (cochlear part) of CN8 - vestibulocochlear nerve

51
Q

What is meant by conduction deafness?

A

Problem conducting sound waves anywhere along the route through the ear, tympanic membrane or ossicles

52
Q

What is meant by sensorineural deafness?

A

Type of hearing loss in which the root cause lies in the inner ear, vestibulocochlear nerve or central auditory processing centres of the brain

Year 2 Term 2 C&M (26 decks)

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