ENT - 2 (ear) Flashcards
what is external acoustic meatus?
the canal from outer ear to tympanic membrane
what nerve supplies anterior auricle (ear) & superior external acoustic meatus & superior tympanic membrane?
CN V3 - mandibular branch of trigeminal
what nerve supplies posterior auricle (ear)?
C 2,3 plexus
- lesser occipital nerve supplies superior part
- greater auricular nerve supplies inferior part
what nerve supplies inferior external acoustic meatus & inferior tympanic membrane?
CN X - vagus
what are the 3 ossicles of middle ear?
- malleus
- incus
- stapes
= they amplify noise
what are 2 muscles in middle ear?
- tensor tympani (reduces amplitude)
- stapedius (reduces vibration of stapes on oval window)
= they dampen sound
what nerve innervates
a) tensor tympani muscle
b) stapedius muscle
a) CN V3
b) CN VII
what are the branches of facial nerve?
- nerve to stapedius
- greater petrosal nerve
- chorda tympani
= branches off in facial canal (before it exits stylomastoid foramen - temporal branch
= branches off after exiting stylomastoid foramen (motor innervation upper face & eyes)
what is route of facial nerve?
passes through internal acoustic meatus - travels through facial canal and then emerges from stylomastoid foramen
what is chorda tympani nerve?
it’s a branch of facial nerve that comes off in facial canal and runs between incus & melleus then leave through tympanic cavity
= supplies anterior 2/3 tongue
what happens if nerve to stapedius damaged?
hyperacusis (increased sensitivity to sound)
- because nerve to stapedius is branch of facial nerve that supplies stapedius muscle (that dampens sound)
what is the pterygopalatine ganglion?
part of autonomic nervous system (involved in parasympathetic system) - gets fibres from greater petrosal nerve (branch of CN VII)
what nerve supplies eustachian tube?
CN IX (glossopharyngeal) via tympanic plexus
*explains why can get otalgia as referred pain from tonsillitis/pharyngitis
what is mastoid aditius?
opening on posterior wall of tympanic cavity connecting middle ear to mastoid antrum
- can mean middle ear infection spread to middle cranial fossa causing osteomyelitis
what is otic capsule?
it’s the whole inner ear thing - has semicircular canals, vestibule, cochlea
where is organ of corti?
organ of corti in cochlear duct, it contains hair cells that detect auditory stimulus
what is the hearing process?
- sound waves vibrate tympanic membrane
- vibrations transmitted through ossicles
- stapes vibrate oval window
- vibration by stapes creates pressure waves in perilymph
- hair cells in cochlea moves, action potential stimulates & conveyed to brain
- pressure waves descend & become vibrations again (dampened at round window)
what is nerve to cochlear & vestibular section of inner ear?
CN VIII = vestibulocochlear nerve
what does facial nerve supply & how can it go wrong?
- lacrimal glands & minor glands
- taste buds
- salivary glands
- muscles of facial expression
= if dysfunction then dry eyes & mucosa, lack of taste anterior 2/3, dry mouth, lack facial expression
what nerve supplies posterior 1/3 tongue and anterior 2/3 tongue?
posterior 1/3 = CN IX
anterior 2/3 = CN V3 (sensory), CN VII (taste)
what is the umbo, pars flaccida & tensa and cone of light on tympanic membrane?
umbo = inwardly depressed part (middle)
pars flaccida = thin superior part
pars tensa = thick lower bit
cone of light = it’s cone of light directed anteroinferiorly when looking in microscope
what is structure of eustachian tube?
anterior 2/3 formed by cartilage
posterior 1/3 formed by bone
what are the 3 fluid filled channels in cochlea?
- scala vestibuli
- scala tympani
- scala media (cochlear duct)
