The Ear

Question 1

what is the external ear comprised of?

Answer 1

cartilaginous pinna (auricle) and external acoustic meatus (ear canal)

Question 2

what marks the medial end of the external acoustic meatus?

Answer 2

tympanic membrane

Question 3

what is the pinna formed of?

Answer 3

elastic cartilage attached to the temporal bone encased in skin

Question 4

where does the cartilage of the pinna gain nutrients from?

Answer 4

the skin

Question 5

what part of the external acoustic meatus is cartilage?

Answer 5

lateral 1/3rd

Question 6

what gland produces earwax?

Answer 6

ceruminous glands

Question 7

what instrument is used to examine the external acoustic meatus and tympanic membrane

Answer 7

otoscope

Question 8

why is the ear pulled posterosuperiorly when examining an adult’s ear using an otoscope?

Answer 8

the external acoustic meatus is curved

Question 9

sensory innervation to the external pinna

Answer 9

C2, 3 spinal nerves
CNV3 (superior EAM and most of tympanic membrane)
CNX (inferior EAM and a bit of tympanic membrane)
CNVII

Question 10

borders of the middle ear

Answer 10

tympanic cavity from the tympanic membrane to the oval window of the inner ear

Question 11

what bones are located in the middle ear?

Answer 11

auditory ossicles (malleus, incus and stapes)

Question 12

role of the ossicles

Answer 12

convey vibration from the tympanic membrane to the apparatus of the inner ear

Question 13

what connects the ossicles?

Answer 13

synovial joints

Question 14

how are the ossicles attached to the wall of the tympanic cavity?

Answer 14

ligaments
mucosal folds (which carry vessels and nerves)

Question 15

two muscles in the tympanic cavity

Answer 15

tensor tympani

stapedius

Question 16

describe the tensor tympani

Answer 16

inserts onto the malleus from eustachian tube, innervated by CNV3
it dampens sound by reducing vibrations from the tympanic membrane (consider oral cavity)

Question 17

describe stapedius

Answer 17

inserts into stapes running from the pyramidal eminence and innervated by CNVII. It reduces vibrations of stapes on the oval window

Question 18

which reflex do both tensor tympani and stapedius have a role in?

Answer 18

acoustic reflex (protection from shouting)

Question 19

what bone is the tympanic cavity located in?

Answer 19

petrous portion of the temporal bone

Question 20

two parts of the tympanic cavity

Answer 20

tympanic cavity proper

epitympanic recess

Question 21

sensory innervation of the mucosa lining the middle ear

Answer 21

CNIX (glossopharyngeal)

Question 22

what does the posterior tympanic cavity contain?

Answer 22

mastoid aditus (opens into the air cells of the mastoid)

Question 23

risk of the mastoid aditus

Answer 23

risk of mastoiditis, osteomyelitis and meningitis

also used as surgical access to the tympanic cavity

Question 24

describe the roof of the tympanic cavity

Answer 24

tegmen tympani is a thin plate of bone separating the middle cranial fossa

Question 25

what is the floor of the tympanic cavity closely related to?

Answer 25

internal jugular vein

Question 26

what does the medial wall of the tympanic cavity contain?

Answer 26

oval window round window promontory facial canal

Question 27

role of the round window

Answer 27

dissipates force from the cochlear

Question 28

what is the promontory

Answer 28

bump from the first turn of the cochlear, tympanic plexus lies over this and is derived from the glossopharyngeal nerve

Question 29

what supplies the parotid gland

Answer 29

lesser petrosal nerve (branch of CNIX)

Question 30

what is the anterior wall of the tympanic cavity closely related to?

Answer 30

carotid canal containing the internal carotid artery eustachian tube chorda tympani

Question 31

what does the eustachian tube connect?

Answer 31

middle ear and nasopharynx (posterior to inferior nasal concha)

Question 32

passage of the chorda tympani in the tympanic cavity

Answer 32

between malleus and incus towards the infratemporal fossa

Question 33

what is the eustachian tube made of?

Answer 33

posterior third is formed by bone while the remainder is cartilaginous (typically collapsed but becomes patent during muscular contraction)

Question 34

role of the eustachian tube

Answer 34

equalise air pressure between the middle ear and nasopharynx

Question 35

what is the mucosa of the middle ear continuous with?

Answer 35

nasal cavity

Question 36

sensory innervation of the mucosa of the middle ear, eustachian tube, nasopharynx, oropharynx and palatine tonsils?

Answer 36

CNIX consider referred otalgia

Question 37

role of the inner ear

Answer 37

reception of sound and maintenance of balance

Question 38

location of the inner ear in terms of the bone

Answer 38

deep within the petrous portion of the temporal bone

Question 39

what does the inner ear consist of?

Answer 39

bony labyrinth (fluid-filled network in the otic capsule) and membranous labyrinth (communicating ducts and sacs)

Question 40

role of the cochlear

Answer 40

hearing

Question 41

role of the SSC, utricle and saccule

Answer 41

balance

Question 42

what is the densest part of the temporal bone?

Answer 42

otic capsule

Question 43

three parts to the bony labyrinth

Answer 43

1. cochlear 2. vestibule 3. semi-circular canals

Question 44

describe the cochlear

Answer 44

shell-shaped spiral cavity encircling a bony core (modiolus) | also have the round window)

Question 45

describe the vestibule

Answer 45

small oval-shaped chamber containing the utricle and saccule (vestibular organs/otolioth organs) also contains the round window

Question 46

what converts mechanical stimuli to neural stimuli in the ear?

Answer 46

mechanoreceptors called hair cells

Question 47

where are the hair cells located?

Answer 47

basilar membrane of the macules of the utricle and saccule and ampullae of the SSC

Question 48

how do APs reach the CNS from hair cells?

Answer 48

travel via the vestibular nerve part of the vestibulocochlear nerve (CNVIII)

Question 49

what are the three fluid-filled channels of the cochlear

Answer 49

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

Question 50

what is the site called where the scala vestibuli and tympani are continuous with each other?

Answer 50

helicotrema

Question 51

what does the modiolus contain?

Answer 51

canals for conveying blood vessels and distributing branches of the cochlear nerve

Question 52

what muscles open the eustachian tube to equalise air pressure?

Answer 52

palatine muscles

Question 53

how can pressure be relieved

Answer 53

valsalva manoeuvres

Question 54

define barotrauma

Answer 54

trauma due to unequalised air pressure

Question 55

what does the tympanic membrane do if atmospheric pressure is more than the tympanic cavity?

Answer 55

pushes inwards

Question 56

what does the tympanic membrane do if the atmospheric pressure is less than the pressure in the tympanic cavity?

Answer 56

membrane pushes out

Question 57

why is otitis media more common in children?

Answer 57

under-developed immune system | shorter distance between middle ear and eustachian tube

Question 58

how does bacteria/viruses spread from the pharynx/tonsils to the middle ear?

Answer 58

eustachian tube

Question 59

steps to show how sound is produced into electrical stimuli

Answer 59

1. sound waves make the tympanic membrane vibrate 2. vibrations are transmitted through ossicles 3. footplate of stapes vibrates in oval window 4. vibrations of stapes creates pressure waves in perilymph 5. hair cells are moved and APs stimulated and conveyed to the brain via the cochlear nerve 6. pressure waves descend and become vibration being dampened at the round window

Question 60

what is the vestibular apparatus responsible for?

Answer 60

balance and perception of head movement

Question 61

what do the semi-circular canals detect

Answer 61

angular movement change - urticle horizontal - saccule vertical

Question 62

what structures pass through the internal acoustic meatus?

Answer 62

facial nerve CNVII vestibulocochlear nerve CNVIII labyrinthine artery (+ veins)-circle of willis