Chapter 9: Anatomy of Hearing

Question 1

pinna

Answer 1

-auricle
-yellow cartilage
-funnel sound
-passive ability to do sound localization

Landmarks: helix, tragus, concha cava, lobule

Question 2

external auditory meatus
-located in what bone?
-where does it terminate? (what structure)
-it is lined with what?

Answer 2

-external ear canal
-osseous portion housed in temporal bone
-terminates at tympanic membrane or eardrum
-it’s a tube so it’s a resonance cavity
-outer portion is lined with fine hair and cerumen (earwax)

Question 3

tympanic membrane
-separates which structures?
-what are its landmarks?

Answer 3

-eardrum
-separates outer ear from middle ear
-made of 3 sheets of layers: outer is continuation of epithelial of EAM, middle is more fibrous, inner is mucosal
Landmarks:
manubrium, umbo (point of attachment for malleus), cone of light - reflects light
-responsible for impedence-matching

Question 4

outer ear pathologies

Answer 4

-otitis externa (swimmer’s ear) - inflammation of the outer ear
-auricular hematoma (cauliflower ear)
-cerumen impaction

Question 5

middle ear
-what bones consist the ossicular chain?

Answer 5

-contains 3 smallest bones in the body (ossicles forming the ossicular chain)
-malleus
-incus
-stapes

Question 6

what is the function of ossicular chain?

Answer 6

together, the malleus-incus-stapes transmit the acoustic energy from the tympanic membrane to the cochlea
-transmits vibration from eardrum to oval window

Question 7

malleus

Answer 7

-largest ossicle
-manubrium provides point of attachment w tympanic membrane
-bulk of bone is head

Question 8

incus

Answer 8

-provides intermediate link of ossicular chain
-articular surface - malleus
-lenticular surface - stapes

Question 9

stapes

Answer 9

-smallest of the three
-footplate presses against oval window

Question 10

tympanic muscles

Answer 10

-stapedius muscle - CN VII - neck of stapes
-tensor tympani - CN V - attached to manubrium

plays a role in stiffening the ossicular chain (dampen sounds)

Question 11

eustachian tube

Answer 11

• keeps the ear dry
• maintain equilibrium between pressure

Question 12

middle ear pathologies

Answer 12

• otitis (inflammation) media
• acute (recent) chronic (long time) serous (fluid)
  -cholesteatoma - buildup of keratin

Question 13

inner ear

Answer 13

• cochlea = hearing
• vestibular system = sense of balance

Question 14

osseous cochlear labyrinth
-what bone is the cochlea embedded in?
-what window is the beginning of when sounds enter into the cochlea?

Answer 14

-embedded inside petrous portion of temporal bone
-oval window is the beginning of when sounds enter into the cochlea
-vibration pushes fluid and bulges the round window
-modiolus - core

Question 15

what do you call the bulge of the middle ear?

Answer 15

cochlear promontory

Question 16

what do you call the fluid in the cochlea on the other side of the oval window?

Answer 16

perilymph

Question 17

where does the perilymph end up?

Answer 17

round window?

Question 18

cochlear anatomy
-it is divided into what 3 structures?
-which structures contain perilymph?
-which structure contain endolymph?
-what other term do you call the scala media?
-what is the scala vestibuli and scala tympani divided by?

Answer 18

divided by 3 = scala vetibuli, scala tympani (perilymph), scala media or cochlear duct (endolymph)

media and tympani are separated by basilar membrane

Question 19

cochlear duct (landmarks)

Answer 19

• scala media
  -houses the organ of corti
  -reissner’s membrane (roof)
  -basilar membrane (floor)

Question 20

organ of corti
-where does hearing take place?
-how many rows of hair cells does it have?
-how many are outer? inner?
-what structure separates the inner and outer hair cells?
-what do you call the cillia sticking out of the hair cells?
-what do you call the membrane on top of the organ of corti?

Answer 20

-where hearing actually takes place in terms of converting mechanical vibrations into electrical signals
-consists of 3 rows of outer hair cells, 1 row of inner hair cell (separated by tunnel of corti), has stereocilia
-above the organ of corti is the tectorial membrane

Question 21

innervation of organ of corti
-what do you call the nerves that go TO and FROM the brain?

Answer 21

-afferent (to brain) - inner
-efferent (from brain) - outer = why? to do readjustments to the frequency

Question 22

basilar membrane
-where is it stiff? base or apex?
-where is the high frequency? where is it low frequency?

Answer 22

base - stiff - so high frequency
apex - floppier - low frequency

Question 23

spiral ganglia
-where do the cell bodies go?

Answer 23

nerve fibers thingy go here

Question 24

conductive hearing loss

Answer 24

• when there’s a problem in any of the structures

Question 25

sensorineural hearing loss

Answer 25

-problem with cochlea

Question 26

vestibular system
-what kind of motion does it detect?

Answer 26

• to detect ROTATIONAL and LINEAR acceleration of the head/neck
• integrates sensory information
• eliminates movement artifacts

Question 27

what are the 3 structures of the vestibular system?

Answer 27

semicircular ducts, vestibule (saccule and utricle), vestibular nuceli

Question 28

what are the 3 semicircular ducts?
-whats their purpose?
-what is at the end of each duct? what fluid is it filled with?

Answer 28

-for detecting ROTATION

1. anterior/superior (nodding yes or no)
2. posterior (tilting head to the side)
3. lateral/horizontal (left or right head movement)

have enlarged ends called ampullae filled with endolymph - has crista or cupula (gelatinous that can bend and there are hair cells sticking up to it)

Question 29

ampulla
-what is it made of?

Answer 29

-made of gelatinous thingy that can flex (cupula)
-there are hair cells

Question 30

vestibular sacs
-what are the 2 sacs called? what is their purpose?
-where are they located?

Answer 30

-utricle and saccule
-for detecting LINEAR acceleration
-located within the ampullae
-deflection of hair cells sends signal

Question 31

function of outer ear

Answer 31

protect ear canal and middle ear

Question 32

what is CN VIII

Answer 32

vestibulocochlear