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3 - HNN > Functional Anatomy of the Ear > Flashcards

Functional Anatomy of the Ear Flashcards

1
Q

State the components of the external ear

A

Pinna, external auditory meatus, lateral surface of tympanic membrane

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2
Q

Describe the structure of the pinna

A

Onenote

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3
Q

Describe the structure of the external acoustic meatus

A
  • Lined with epithelial cells which can migrate and shed out of ear
  • Sigmoid shape - need to pull ear up and back to straighten when examining
  • Cartilaginous (outer 1/3) and body part (inner 2/3)
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4
Q

Outline the role of hair and wax in the ear canal

A
  • Arrangement of hairs and production of wax in cartilaginous part
    • Prevent objects entering deeper into ear canal
    • Also aid in desquamation (shedding) and skin migration out of canal
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5
Q

State the components of the middle ear

A

Ossicles and air filled cavity between tympanic membrane and inner ear

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6
Q

State the components and role of ossicles

A
  • Malleus, incus, stapes
  • Connected via synovia joints and amplify vibrations from the tympanic membrane to the oval window of the cochlea
  • Transmitting vibration from an air medium to a fluid-medium
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7
Q

Outline the role of muscles within the middle ear

A
  • Tensor tympani and stapedius muscle within middle ear
    • Muscles contract if potentially excessive vibration due to loud noise (protection, acoustic reflex)
    • Stapedius supplied by facial nerve
      - Can get hyperacousis if facial nerve damage
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8
Q

Outline the role of the pharyngotympanic tube

A
  • Pharyngotympanic / Eustachian tube equilibrates pressure of middle ear with atmospheric pressure
  • Mucous membrane of middle ear continuously reabsorbs air in middle ear causing negative pressure
  • Tube allows equilibration of pressure within middle ear cavity with that of atmosphere
  • Allows for ventilation of and drainage of mucus from the middle ear
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9
Q

Which nerves run through the middle ear

A
  • Facial nerve and chorda tympani runs through middle ear cavity
  • Facial nerve may be involved in pathology involving the middle ear
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10
Q

State the components of the inner ear

A

Vestibular apparatus and cochlea - fluid filled tubes

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11
Q

Describe the role of the cochlea

A
  • Cochlea converts vibration into an electrical signal (action potential) which is perceived as sound
  • Movements at the oval window set up movements of the fluid in the cochlea
  • Waves of fluid cause movement of special sensory cells (stereocilia) within the cochlear duct which generate action potential in CN VIII
  • Round window helps to relieve the pressure created from oval window vibration
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12
Q

Outline the role of the vestibular apparatus

A
  • Vestibular apparatus / semicircular canal is involved in maintaining our sense of position and balance
  • Includes the semicircular ducts, the saccule and utricle
  • Fluid filled series of channels and sacs that respond to position and rotation and maintain our sense of balance
    - Channels and sacs located at different planes
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13
Q

What is otalgia

A

Ear pain

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14
Q

Describe Ramsay Hunt syndrome

A
  • Shingles of facial nerve
  • VZV infection or reactivation involving geniculate ganglion of CN VII
  • Ipsilateral facial drooping
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15
Q

Desscribe the cause and treatment to pinna haematoma

A
  • Secondary to blunt injury to the pinna - common in contact sports
  • Accumulation of blood between cartilage and perichondrium
    • Perichondrium supplies blood to cartilage
  • Deprives the cartilage of its blood supply, causing avascular necrosis of tissue
  • Treatment - prompt drainage
    • Measures to prevent re-accumulation and re-apposition of two layers
  • Untreated or poorly treated leads to fibrosis and new asymmetrical cartilage development
    • Cauliflower ear
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16
Q

Describe otitis externa and its treatment

A
  • Swimmers ear
  • Small/red ear canal
  • Inflammation of external ear
  • Can be infection / problems with skin (eczema)
  • Treatment - ear drops
17
Q

Describe causes of tympanic membrane abnormalities

A
  • Perforation due to jabbing or build up of pressure in middle ear cavity
  • Bulging secondary to otitis media due to middle ear infection could lead to perforation
18
Q

Describe otosclerosis

A
  • Ossicles can become fused at articulations, in particular between base plate of stapes and oval window
  • Sound vibrations cannot be transmitted
  • Causes deafness
19
Q

Describe the cause and appearance of otitis medial with effusion

A
  • Glue ear
  • Not an actual infection
  • Build up of fluid and negative pressure in middle ear
  • Due to Eustachian tube dysfunction - can predispose to infection
  • Decreases mobility of tympanic membrane and ossicles - affects hearing
  • Most resolve spontaneously in 2-3 months
    • Require grommets (tympanostomy tube) to ventilate middle ear - equilibrates pressure
  • Tympanic membrane looks retracted as sucked in due to negative pressure of middle ear
20
Q

Describe the presentation and typical age of acute otitis media

A
  • Acute middle ear infection
  • More common infants/children than in adults
    • Pharyngotympanic tube is shorter and more horizontal in infants
    • Easier for infection from the nasopharynx to the middle ear
    • Tube can block more easily, compromising ventilation and drainage of middle ear - increases risk of middle ear infection
  • Otalgia - infants may pull or tug at the ear
  • Red +/- bulging tympanic membrane and loss of normal landmarks
21
Q

Discuss the complications of acute otitis media

A
  • Tympanic perforation
  • Facial nerve involvement
  • Rarer but potentially life-threatening complications include
    • Mastoiditis
      • Middle ear cavity communicates via mastoid antrum with mastoid air cells
      • Provides a potential route for middle ear infections to spread into the mastoid bone (mastoid air cells)
      • Presents with ear pushed forward due to swollen infection behind ear
    • Intracranial complications - meningitis, sigmoid sinus thrombosis, brain abscess
22
Q

Describe the presentation and cause of cholesteatoma

A
  • Abnormal skin growth growing into middle ear, behind the tympanic membrane
  • Causes painless, often smelly otorrhea (ear discharge) and possible hearing loss
    • Potentially more serious neurological complications
  • Usually secondary to chronic Eustachian tube dysfunction or chronic/recurring ear infections
    • Can block Eustachian tube
  • Not malignant but slowly grows and expands - eroding into structures such as ossicles, mastoid bone, cochlea
23
Q

Describe the cause of presentation of Meneire’s Disease

A
  • Causes attacks of dizziness with a spinning sensation (vertigo), hearing loss and tinnitus
  • Comes in attacks/episodes
  • Due to build up of fluid in the inner ear
    • Increased pressure of fluid can lead to dull hearing
    • Vertigo due to fluid triggering stereocilia to release action potential telling the body it is moving
  • Vertigo, hearing problem
24
Q

Briefly describe benign paroxysmal positional vertigal (BPPV)

A
  • Short episodes of intense vertigo when moving head in certain directions
  • Solid crystals in the vestibular apparatus
    - Moves stereocilia inside which conveys movement of person to brain
25
Q

What is labyrinthitis

A
  • Inner ear infection

- Symptoms - vertigo, feeling sick, hearing loss

26
Q

Outline the steps as to how we hear

A
  1. Pinna and external auditory canal focuses and funnels sound waves towards tympanic membrane which vibrates
  2. Vibration of the ossicles (stapes at the oval window) sets up vibrations/movement in cochlear fluid
  3. Sensed by stereocilia in spiral organ of Corti of the cochlear duct
  4. Movement of the stereocilia in organ of Corti trigger action potentials in cochlear part of CN VIII
  5. Signal travels to primary auditory cortex
27
Q

Differentiate between conductive and sensorineural hearing loss

A
  • Conductive hearing loss - pathology involving the external or middle ear
  • Sensorineural hearing loss - pathology involving the inner ear structures of CN VIII
28
Q

List examples of conductive hearing loss

A
  • Wax
  • Otitis media
  • Glue ear / otitis media with pleural effusion
  • Otosclerosis
29
Q

List example of sensorineural hearing loss

A
  • Presbyacusis (old age hearing loss)
  • Meniere’s disease
  • Acoustic neuroma - benign tumour of vestibulocochlear nerve
  • Ototoxic medications
30
Q

Describe the Rinne’s and Weber’s test

A
  • Rinne’s test
    • Ring and place tuning fork over mastoid process (behind ear) and then in front of ear
    • Positive test - should be loudest in front (air conduction > bone conduction)
  • Weber’s test
    • Ring and place tuning fork on forehead or and top of head
      • Positive test - sound should be equal in both ears
31
Q

Describe the result of the Rinne’s and Weber’s test in conductive hearing loss

A
  • Rinne’s test shows that sound is louder from the bone
    • Bypasses blocked ear canal
  • Weber’s test shows that sound is louder in affected ear
    • Affected ear blocks off background sound so louder
      • Restricted hearing so only hear significant sound
32
Q

Describe the result of the Rinne’s and Weber’s test in sensorineural hearing loss

A
  • Rinne’s test is positive
    • However both ears will have quieter sound
  • Weber’s test shows that sound is louder in normal ear
    - Affected ear has restricted hearing so background noise quieter
33
Q

Be familiar with the steps of examining the external ear, external auditory meatus and tympanic membrane using an otoscope

A
  • Sit to the side of the patient
  • Straighten the external auditory canal by pulling the pinna up, out and back
    • In a child, the canal should be straightened by pulling the pinna down and back
  • The external auditory canal is only 2.5cm in length, and thus the otoscope should not be inserted very deep
34
Q

Describe the features of a tympanic membrane on otoscopic examination

A

Onenote

35
Q

How do you tell if a tympanic membrane view through otoscope is left or right ear

A

Cone of light and handle of malleus are on the right for the right ear and on the left for the left ear

3 - HNN (15 decks)

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