Ear Flashcards
What is the auricle and how does it function in hearing?
shell-shaped flap of skin-covered cartilage.
Auricle directs sound waves into external acoustic meatus.
The ridges of the auricle are spaced to reinforce sounds in the 1-3kHz range (human speech)
What is the external acoustic meatus and how does it function in hearing?
2-3 cm canal between auricle and TM.
Directs sound pressure waves to TM.
What is the tympanic membrane and how does it function in hearing?
1 cm diameter oval between external acoustic meatus and tympanic cavity.
Vibrates in response to sound wave striking its surface; vibrations are transmitted to the middle ear ossicles.
What innervates the auricle?
greater auricular nerve from cervical plexus
auriculotemporal from V3 of trigeminal
What innervates the tympanic membrane?
external tympanic membrane: auriculotemporal of V3, auricular branch of CN X
internal tympanic membrane: CN IX
What bone encloses the middle ear?
petrous part of temporal bone
What are the contents of the tympanic cavity?
3 ossicles
2 skeletal muscles
2 nerves
1 nerve plexus
What nerve transits the tympanic cavity?
CN VII chorda tympani
What provides sensory innervation to the eustachian tube?
CN IX via tympanic plexus (posterior tube)
V2 (anterior tube)
What are the 3 auditory ossicles, from lateral to medial?
lateral to medial: malleus, incus, stapes
What passes medial to the neck of the malleus?
chorda tympani
What kind of joints unite the ossicles?
synovial
What is the function of the tensor tympani muscle?
reduces the amplitude of the movements of the MALLEUS
What nerve innervates the tensor tympani?
nerve to tensor tympani, a branch of V3
TTT: Trigeminal Tensor Tympani
What is the function of the stapedius muscle?
prevents excessive movements of the STAPES
What nerve innervates the stapedius muscle?
nerve to the stapedius, a branch of CN VII
SS: Seven Stapedius
What structures in the middle ear are innervated by the chorda tympani?
NONE - chorda tympani is just passing through!
What are the 2 nerves in the middle ear?
- tympanic nerve (CNIX)
2. chorda tympani
What is the nerve plexus in the middle ear?
tympanic plexus
What structures are innervated by fibers from the tympanic plexus?
sensation to the middle ear and most of the pharyngotympanic (eustachian) tube
What is the composition of the perilymph?
high sodium, low potassium, like most extracellular fluids of the body
What is the composition of the endolymph?
high potassium, low sodium - unique extracellular fluid!!
What is the function of the utricle and saccule?
To perceive static head position via otoliths:
utricle = horizontal hair cells; saccule = vertical hair cells
What innervates the hair cells of the utricle and saccule?
vestibular division of vestibulocochlear nerve CN VIII
How do we perceive dynamic rotational movements of the head?
hair cells in the semicircular canals
What innervates the hair cells of the semicircular canals?
vestibular division of the vestibulocochlear nerve CN VIII
How do we hear?
Sound waves in air strike the TM, pass through the ossicles, and reach the base of the stapes in the oval window of the middle ear.
Movements of the oval window create waves in the perilymph of the scala vestibuli and displace the cochlear duct.
Hair cells in the Organ of Corti are activated.
What nerve innervates the hair cells of the Organ of Corti?
cochlear division of vestibulocochlear nerve CN VIII
What artery supplies the auricle?
external carotid
