anatomy Flashcards
which nerves innervate the external acoustic meatus?
CN V3 = superior part + most of tympanic membrane
CN X(vagus) = inferior part + a bit of tympanic membrane
shape of external acoustic meatus in kids vs adults?
kids = short + straight, pull posteroinferiorly to see
adult = curved, pull auricle posterosuperiorly
what type of joints are present in the middle ear?
synovial - allow for smooth movement
ossicles are suspended from tegmen tympani by ligaments
ossicles decrease in size lateral to medial - amplification
how does the stapes of the middle ear communciate with the inner ear?
oval window
2 muscles of middle ear + their innervations
tensor tympani muscle (CN V3) stapedius muscle (CN VII facial)
both play roles in the acoustic reflex
tensor tympani muscle
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
stapedius muscle
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)
how does atmospheric pressure compare to that of the middle ear? how is pressure equalised?
same pressure
palate muscles open the eustachian tube to equalise pressure
where does the eustachian tube open into? what innervates this area?
connects anterior wall of middle ear cavity to nasopharynx –> how otitis media spreads
innervation = CN IX glossopharyngeal (also supplies oropharynx)
what conveys general sensation to the tympanic cavity? describe the route of this ?
tympanic branch of CN IX
tympanic plexus lies over promontory (bump from cupula)
general sensory axons from tympanic plexus will pass down Eustachian tube
how can damage to tympanic area cause parotid gland dysfunction?
tympanic plexus (found in tympanic cavity) becomes the lesser petrosal nerve which is the parotid glands autonomic nerve supply
what is the clinical significance of the mastoid aditus?
provides surgical access to tympanic cavity - caution lies close to facial nerve canal
infection/inflammation can cause mastoiditis
location of matoid aditus
posterior wall of epitympanic recess in middle ear
what are the 2 labyrinths of the inner ear and how do they differ?
bony labrith - filled with PERIlymph, similar to extracellular fluid
membranous labyrinth - suspended within bony labyrinth, filled with ENDOlymph, similar to intracellular fluid
what is the helicotrema?
cochlear apex where the scala tympani + scala vestibule meet
(top/end of swirl)
communications between oval + round window
what part of the vestibular apparatus detects angular movement change?
semicircular ducts
- anterior - nodding head, sagittal
- lateral - shaking head, axial
- posterior - ear to shoulder, coronal
what parts of the vestibular apparatus detects linear movement change?
utricle = horizontal
saccule = vertical
what happens in the semicircular canals on head movement?
ampullae of the semicircular canals have internal crests with hair cell clusters
head movement moves hair cells RELATIVE TO the endolymph –> causes depolarisation
what would happen if the cochlear nerve was cut, vestibular nerve was cut and the internal acoustic meatus blocked respectively?
Cut cochlear nerve = lose hearing
Cut vestibular = lose balance on that side
Block internal acoustic meatus = lose both
what 3 things pass through the internal acoustic meatus?
CN VII (facial nerve) CN VIII (vestibulocochlear nerve)
labyrinthine artery (+veins) --> from circle of Willis
what 2 nerves does the chorda tympani connect?
facial + linguinal (CN V3 branch)
course of chorda tympani
branches from facial nerve in facial canal
courses between incus + malleus
leaves tympanic cavity via petrotympanic fissure
what does the greater petrosal nerve innervate?
the lacrimal gland
branch of facial nerve
where do the preganglionic parasympathetic axons of the greater petrosal nerve synapse?
in the pterygopalatine ganglion
damage to the greater petrosal nerve would cause what symtpoms?
dry eye
dry mucosa
damage to proximal linguinal + proximal chorda tympani would cause what symptoms respectively?
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
where does facial nerve leave the temporal bone?
through stylomastoid foramen
innervation of tongue
anterior 2/3
- general sensory = CN V3
- taste = CN VII
posterior 1/3
- general sensory + taste = CN IX
where is the pterygopalatine fossa found?
between sphenoid bone + maxilla
the greater petrosal and deep petrosal nerve combine to become what? what is this contained in?
the vidian nerve
found in the pterygoid canal
what is the pterygopalatine ganglion?
parasympathetic ganglion of the facial nerve (CN VII)
what part of the tongue is responsible for touch + temp (no taste buds)?
filiform papillae
what is the area in the nose called where damage/perforation to this area would cause epistaxis?
Kiesselbach’s plexus (little’s area)
inputs from branches of opthalmic, maxillary + facial artery
where does the ophthalmic artery branch from? what 2 branches of the ophthalmic artery contribute to epistaxis?
internal carotid
anterior + posterior ethmoidal arteries
–> pass through ethmoidal bone, both bilaterall arteries
where does the maxillary artery branch from?
external carotid artery
what 2 branches of the maxillary artery contribute to epistaxis? course of these arteries?
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
what branch of the facial artery contributes to epistaxis?
septal branch of superior labial artery
external carotid -> facial -> superior labial
5 inputs to Kiesselbach’s plexus
ophthalmic 1. anterior ethmoidal 2. posterior ethmoidal facial 3. septal branch of superior labial artery maxillary 4. greater palatine 5. sphenopalatine
describe the course of the glossopharyngeal nerve?
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)
what passes throught the foramen ovale?
mandibular division of trigeminal nerve
how do V1 + V2 differ from V3?
all do sensory innervation
ONLY V3 does motor as well - muscle of mastication
V1 - superior orbital fissure
V2 - foramen rotundum
V3 - foramen ovale
