Anatomy and Pathophysiology of the Ear

Question 1

why do STs have to learn about ear and hearing

Answer 1

to identify hearing loss:

• affects speech perception
• may cause comm breakdown
• affects production of speech

Question 2

what is the auditory hierarchy

Answer 2

1. detection
2. discrimination
3. identification
4. comprehension

Question 3

where does comm breakdown start

Answer 3

identification

Question 4

why do we need to know about hearing

Answer 4

human interactions rely heavily on verbal comm

- underpinned by HEARING ability

Question 5

what do we hear with

Answer 5

1. ear: peripheral auditory system (audiologist)

2. brain: central auditory nervous system (slt)

Question 6

what can the human ear be divided into

Answer 6

1. outer ear
2. middle ear
3. inner ear

Question 7

what does outer ear anatomy compose of

Answer 7

1. pinna (auricle)
2. concha
3. external auditory meatus (external auditory canal)

Question 8

what is the composition of the external auditory meatus

Answer 8

outer 1/3 cartilage

inner 2.3 bone

Question 9

what is the outer ear function

Answer 9

pinna: funnel sounds towards external auditory meatus
concha: enhance intensity of sound that arrives at eardrum

external auditory meatus

• directs sound to eardrum
• secrete earwax
• tiny hairs directed outward

Question 10

what are some outer ear pathology

Answer 10

1. congenital abnormality
   - stenotic ear canal
   - microtia
   - treacher-collins syndrome
   - goldenhar syndrome
   - pfeiffer syndrome
   - crouzon syndrome
2. perichondritis (infection)
3. blockage of ear canal
   - impacted ear wax
   - otitis externa
   - foreign body

Question 11

what does middle ear anatomy compose of

Answer 11

1. tympanic membrane (eardrum)
2. ossicles - malleus, incus, stapes
3. eustachian tube

Question 12

what can be seen in healthy tympanic membranes

Answer 12

handle of malleus and CONE OF LIGHT

Question 13

what does 5 o clock cone of light mean

Answer 13

right ear

Question 14

what does 7 o clock cone of light mean

Answer 14

left ear

Question 15

are the ossicles the smallest bones in the body

Answer 15

yes! (and they never grow)

Question 16

what does the eustachian tube connect

Answer 16

ME to nasopharynx

Question 17

what is the composition of the eustachian tube

Answer 17

1/3 bone

2/3 cartilaginous

Question 18

how is the movement of the eustachian tube

Answer 18

closed at rest

opens with yawning or swallowing

Question 19

why do young children with URTI tend to have OME

Answer 19

Infant’s eustachian tube is shorter and horizontal

• tube may get swollen and not work as efficiently
• harder for the tube to clear out fluid build-up
• impinge pressure on eardrum -> pain and hearing impacted

Question 20

what is the function of the ossicles

Answer 20

1. pre-cochlear amplification system through 3 transformer mechanisms
2. protective mechanism through acoustic reflex

Question 21

how does pre-cochlear amplification take place

Answer 21

1. area ratio advantage
   - tympanic membrane (17) - larger area and lower pressure
   - footplate of stapes (1) - smaller area and higher pressure
2. lever advantage by bones (malleus and incus)
   - force is increased by a factor of 1.3
3. ‘buckling’ advantage by concave structure of TM
   - small displacement at malleus -> great gain at stapes

Question 22

why is a pre-cochlear amplification system needed

Answer 22

sound waves travel from air to solid bones to fluid -> some energy may be lost

Question 23

how does protective mechanism take place

Answer 23

contraction of stapedius and tensor tympani muscles in ME to attenuate hi intensity of sound

Question 24

what is the function of the eustachian tube

Answer 24

1. ventilation: equalise pressure in ME
2. clearance: drainage of secretions
3. protection: prevention of reflux

Question 25

what are some examples of middle ear pathology

Answer 25

1. middle ear cavity - perforated eardrum - tympanosclerosis - cholesteatoma 2. middle ear cavity with effusion - chronic otitis media - otitis media with effusion

Question 26

what does inner ear anatomy compose of

Answer 26

1. balance organ (vestibular system) | 2. hearing organ (auditory system)

Question 27

what is present in the cochlea

Answer 27

- basilar membrane - scala vestibuli - scala media - scala tympani - OHC - IHC - organ of corti

Question 28

how does the inner ear function

Answer 28

1. vibration along basilar membrane deflects hair cells 2. hair cells convert mechanical vibration of sound into electrical energy 3. electrical energy sent via hearing nerve to the brain

Question 29

how does the tonotopic mapping happen in the cochlea

Answer 29

- hi freq sounds at the basal end | - lo freq sounds at the apical end

Question 30

what are some examples of inner ear pathology

Answer 30

1. damaged hair cells (trauma, noise, age) | 2. cochlea malformation

Question 31

what is CHL

Answer 31

when transduction of sound is blocked in outer and/or middle ear

Question 32

is CHL permanent

Answer 32

no

Question 33

what is SNHL

Answer 33

when transduction of sound is affected in inner ear and/or auditory nerve

Question 34

is SNHL permanent

Answer 34

yes

Question 35

what is MHL

Answer 35

HL result of pathology of outer ear, ME and inner ear