anatomy

Question 1

which nerves innervate the external acoustic meatus?

Answer 1

CN V3 = superior part + most of tympanic membrane

CN X(vagus) = inferior part + a bit of tympanic membrane

Question 2

shape of external acoustic meatus in kids vs adults?

Answer 2

kids = short + straight, pull posteroinferiorly to see

adult = curved, pull auricle posterosuperiorly

Question 3

what type of joints are present in the middle ear?

Answer 3

synovial - allow for smooth movement

ossicles are suspended from tegmen tympani by ligaments
ossicles decrease in size lateral to medial - amplification

Question 4

how does the stapes of the middle ear communciate with the inner ear?

Answer 4

oval window

Question 5

2 muscles of middle ear + their innervations

Answer 5

tensor tympani muscle (CN V3)
stapedius muscle (CN VII facial)

both play roles in the acoustic reflex

Question 6

tensor tympani muscle

Answer 6

found in middle ear - runs from cartilaginous portion of eustachian tube to handle of malleus

dampens sound by reducing vibrations of tympanic membrane (reduces noise of chewing)

innervation = CN V3

Question 7

stapedius muscle

Answer 7

found in middle ear - runs from pyramidal eminence to neck of stapes

dampens sound by reducing vibrations of stapes on oval window

innervation = CN VII (facial nerve)

Question 8

how does atmospheric pressure compare to that of the middle ear? how is pressure equalised?

Answer 8

same pressure

palate muscles open the eustachian tube to equalise pressure

Question 9

where does the eustachian tube open into? what innervates this area?

Answer 9

connects anterior wall of middle ear cavity to nasopharynx –> how otitis media spreads

innervation = CN IX glossopharyngeal (also supplies oropharynx)

Question 10

what conveys general sensation to the tympanic cavity? describe the route of this ?

Answer 10

tympanic branch of CN IX
tympanic plexus lies over promontory (bump from cupula)

general sensory axons from tympanic plexus will pass down Eustachian tube

Question 11

how can damage to tympanic area cause parotid gland dysfunction?

Answer 11

tympanic plexus (found in tympanic cavity) becomes the lesser petrosal nerve which is the parotid glands autonomic nerve supply

Question 12

what is the clinical significance of the mastoid aditus?

Answer 12

provides surgical access to tympanic cavity - caution lies close to facial nerve canal

infection/inflammation can cause mastoiditis

Question 13

location of matoid aditus

Answer 13

posterior wall of epitympanic recess in middle ear

Question 14

what are the 2 labyrinths of the inner ear and how do they differ?

Answer 14

bony labrith - filled with PERIlymph, similar to extracellular fluid

membranous labyrinth - suspended within bony labyrinth, filled with ENDOlymph, similar to intracellular fluid

Question 15

what is the helicotrema?

Answer 15

cochlear apex where the scala tympani + scala vestibule meet
(top/end of swirl)

communications between oval + round window

Question 16

what part of the vestibular apparatus detects angular movement change?

Answer 16

semicircular ducts

• anterior - nodding head, sagittal
• lateral - shaking head, axial
• posterior - ear to shoulder, coronal

Question 17

what parts of the vestibular apparatus detects linear movement change?

Answer 17

utricle = horizontal

saccule = vertical

Question 18

what happens in the semicircular canals on head movement?

Answer 18

ampullae of the semicircular canals have internal crests with hair cell clusters

head movement moves hair cells RELATIVE TO the endolymph –> causes depolarisation

Question 19

what would happen if the cochlear nerve was cut, vestibular nerve was cut and the internal acoustic meatus blocked respectively?

Answer 19

Cut cochlear nerve = lose hearing
Cut vestibular = lose balance on that side
Block internal acoustic meatus = lose both

Question 20

what 3 things pass through the internal acoustic meatus?

Answer 20

CN VII (facial nerve)
CN VIII (vestibulocochlear nerve)

labyrinthine artery (+veins)
--> from circle of Willis

Question 21

what 2 nerves does the chorda tympani connect?

Answer 21

facial + linguinal (CN V3 branch)

Question 22

course of chorda tympani

Answer 22

branches from facial nerve in facial canal
courses between incus + malleus
leaves tympanic cavity via petrotympanic fissure

Question 23

what does the greater petrosal nerve innervate?

Answer 23

the lacrimal gland

branch of facial nerve

Question 24

where do the preganglionic parasympathetic axons of the greater petrosal nerve synapse?

Answer 24

in the pterygopalatine ganglion

Question 25

damage to the greater petrosal nerve would cause what symtpoms?

Answer 25

dry eye | dry mucosa

Question 26

damage to proximal linguinal + proximal chorda tympani would cause what symptoms respectively?

Answer 26

proximal linguinal = dry mouth (secretkmotor supply) proximal chorda tympani = lack of taste to anter 2/3 of tongue damage to distal (where they join = loss of both

Question 27

where does facial nerve leave the temporal bone?

Answer 27

through stylomastoid foramen

Question 28

innervation of tongue

Answer 28

anterior 2/3 - general sensory = CN V3 - taste = CN VII posterior 1/3 - general sensory + taste = CN IX

Question 29

where is the pterygopalatine fossa found?

Answer 29

between sphenoid bone + maxilla

Question 30

the greater petrosal and deep petrosal nerve combine to become what? what is this contained in?

Answer 30

the vidian nerve | found in the pterygoid canal

Question 31

what is the pterygopalatine ganglion?

Answer 31

parasympathetic ganglion of the facial nerve (CN VII)

Question 32

what part of the tongue is responsible for touch + temp (no taste buds)?

Answer 32

filiform papillae

Question 33

what is the area in the nose called where damage/perforation to this area would cause epistaxis?

Answer 33

Kiesselbach's plexus (little's area) inputs from branches of opthalmic, maxillary + facial artery

Question 34

where does the ophthalmic artery branch from? what 2 branches of the ophthalmic artery contribute to epistaxis?

Answer 34

internal carotid anterior + posterior ethmoidal arteries --> pass through ethmoidal bone, both bilaterall arteries

Question 35

where does the maxillary artery branch from?

Answer 35

external carotid artery

Question 36

what 2 branches of the maxillary artery contribute to epistaxis? course of these arteries?

Answer 36

sphenopalatine artery - covers a lot of vomer bone greater palatine artery -> descending palatine artery then follows hard palate inferiorly moving anterior then up through hard palate to enter plexus

Question 37

what branch of the facial artery contributes to epistaxis?

Answer 37

septal branch of superior labial artery external carotid -> facial -> superior labial

Question 38

5 inputs to Kiesselbach's plexus

Answer 38

``` ophthalmic 1. anterior ethmoidal 2. posterior ethmoidal facial 3. septal branch of superior labial artery maxillary 4. greater palatine 5. sphenopalatine ```

Question 39

describe the course of the glossopharyngeal nerve?

Answer 39

leaves CNS at upper medulla oblongata passes through jugular foramen (hole beside magnum) enters parapharyngeal space + lays on stylopharyngeus muscle (somatic motor supply to stylopharngeus)

Question 40

what passes throught the foramen ovale?

Answer 40

mandibular division of trigeminal nerve

Question 41

how do V1 + V2 differ from V3?

Answer 41

all do sensory innervation ONLY V3 does motor as well - muscle of mastication V1 - superior orbital fissure V2 - foramen rotundum V3 - foramen ovale