Control L18 auditory pathways Flashcards
What parts of the skull are related to the ear’s location?
externally:
squamous part of temporal bone
external auditory meatus (canal)
mastoid process
internally:
squamous part of temporal bone
petrous part of temporal bone
internal auditory meatus (canal)
What cranial nerves travel through the internal auditory meatus?
CN VII and VIII
What is the function of the external ear?
auricle receives sound waves and funnels them to the external acoustic canal
what is the function of the middle ear?
Transformation of sound waves into mechanical waves/vibrations
what is the function of the inner ear?
conversion of mechanical waves into electrical waves/signals
what is the anatomical name for the eardrum?
the tympanic membrane
what is the middle ear?
an air filled space in the petrous part of the temporal bone. seperated from external ear by tympanic membrane
what bones are found in the middle ear?
the ossicles - malleous, incus and stapes (closer to outer –> closer to inner ear)
how does the middle ear communicate with the nasopharynx?
the pharyngotympanic tube aka eustachian tube
why are middle ear infections more common in infants?
as the pharyngotympanic tube is positioned quite flat so infection spreads easier than in an adult who has a more angled pharyngotympanic tube where gravity prevents infection moving up into the ear easily
what is the role of the pharyngotympanic tube?
equalise pressure between internal environment and atmospheric pressure
why is the middle ear a high risk space for infections/spread of infection?
has close relationships with other surrounding structures:
- with nasopharnyx via pharnygotympanic tube
- with cranial cavity (specifically middle cranial fossa) via mastoid air cells
- with IJV which lies inferiorly so risk of thrombosis
- internal carotid artery which lies anteriorly and can lead to pulsatile tinitis
- facial muscles and tongue via facial nerve as middle ear is transversed by chorda tympani and facial canal.
- parotid gland via lesser petrosal nerve
- inner ear via the oval window
what are the two special sense organs in the inner ear?
the vestibular system
cochlear system and cochlear ducts
what is the role of the vestibular system?
maintain balance and equilibrium
what is the vestibular system formed of?
vestibule
semicircular canal
semicicrular ducts
what nerve supplies the vestibular system?
vestibular nerve
how is the cochlear organised?
tonotopically - highest frequency sounds/pitch received at base and gets lower towards apex
what nerve supplies the cochlear system?
cochlear nerve
what nerve does the cochlear and vestibular nerve develop from?
CN VIII - vestibulocochlear
what is the function of the cochlear system?
hearing