4.6 Ear Flashcards
What structures make up the external ear?
pinna and external acoustic meatus
What ossicle is attached to the deep surface of the tympanic membrane?
malleus
What muscle attaches to the malleus and what innervates it?
tensor tympani m. (CN V3)
What does the stapes attach to?
oval window of cochlea
What muscle attaches to the stapes and what innervates it?
stapedius m. (CN VII)
What compromises the bony labyrinth of the inner ear?
vestibule, semicircular canals and cochlea
What is the bony labyrinth filled with?
perilymph
What is the membranous labyrinth filled with?
endolymph
What nerve supplies the external surface of the tympanic membrane?
auricular branch (CN X)
What nerve supplies the internal surface od the tympanic membrane?
tympanic n. (CN IX)
What separates the external from the middle ear?
tympanic membrane
Which portion of the mandible can be palpated by placing the small finger into the out part of the external ear canal?
mandibular condyle
What nerve passes between the malleus and the incus?
Chorda tympani (CN VII)
What is the function of the oval window?
translates mechanical vibrations of ossicles into waves of fluid that fills cochlea
What is the function of the round window?
dissipates pressure waves generated by mechanical vibrations
How does the oval window relate to the promontory?
near upper pole of promontory
How does the round window relate to the promontory?
near lower pole of promontory
What structure forms the promontory?
initial part of spiral bony cochlea, bulges into middle ear cavity in form of round projection on medial wall of cavity
Tensor tympani m. (V3) attaches to the malleus to dampen excessive vibration of membrane caused by loud sound including …
mastication noise
Stapedius m. (CN VII) attaches to the stapes and reduces excessive vibration of stapes caused by loud sound including …
own voice
What fiber types are found in the tympanic branch of CN IX?
general sensory - mucosa of middle ear cavity and inner surface of tympanic membrane
Preganglionic parasympathetic fibers of lesser petrosal n.
The lesser petrosal n. exits the middle ear cavity through hiatus of lesser petrosal canal and enters the middle cranial fossa and then exits the cranial cavity through?
foramen ovale
Where does the lesser petrosal n. synapse?
otic ganglion
What nerve do the postganglionic parasympathetic fibers of the lesser petrosal n. hitch a ride on after synapsing in the otic ganglion?
auriculotemporal n. of (CN V3) to the parotid gland
What does the middle ear communicate with posteriorly?
mastoid air cells (deep to mastoid process)
What does the middle ear communicate with anteriorly?
nasopharynx via bony and cartilaginous pharyngotympanic tube
What does the lateral wall of the middle ear communicate with?
tympanic membrane
What does the medial wall of the middle ear communicate with?
has bony projections caused by lateral semicircular canal, facial canal, and cochlea (cochlear promontory)
What component of the vestibule detects position of head in space (tilt of head) by detecting gravitational pull with its horizontally oriented patch of receptors (macula)?
utricle
What component of the vestibule detects vertical acceleration with its vertically oriented patch of receptors (macula)?
saccule
Both components of the vestibule are responsible for what kind of balance?
static
What is the role of the semicircular canals?
detects angular acceleration of head in each plane
Hair cells embedded in … detect flow of endolymph in each semicircular canal generated by inertia caused by head rotation in a given plane
cupula on ampulla
What kind of balance are the semicircular canals responsible for?
kinetic balance
What fluid is found in the scala vestibule and scala tympani?
perilymph
What is the upper portion of the bony cochlea, with a vestibular membrane?
scala vestibuli
What is the power portion of the bony cochlea with its basilar membrane?
scala tympani
What is the name of the narrow passageway where the two scalae communicate near the apex of the cochlea?
helicotrema
What does the internal acoustic meatus have perorations for?
CN VII, CN VIII, and vasculature
After entering the internal acoustic meatus, CN VII makes a 90-degree turn posteriorly at the location of …
geniculate ganglion
What does the facial n. (VII) give off after the geniculate ganglion?
greater petrosal n. (to middle cranial fossa) and continues in the bony facial canal to give off nerve to stapedius, and chorda tympani n., before exiting through the stylomastoid foramen
What region of the external ear does the great auricular n. (C2-3) innervate?
lower half anteriorly and posteriorly
What region of the external ear does the lesser occipital n. (C2-3) innervate?
posterior upper part of the auricle and the adjacent cranial surface
What region of the external ear does the auriculotemporal n. (V3) innervate?
anterior upper part of the auricle (tragus) and the adjacent temporal skin, and anterior external acoustic meatus
What region of the external ear does the auricular branch of CN X innervate?
posterior external acoustic meatus and external surface of tympanic membrane
