Lecture 31b Flashcards
Three parts of the ear/vestibulocochlear organ
- external ear
- middle ear
- internal ear
External ear parts
- auricle/pinna
- external acoustic meatus
Different parts of auricle/pinna
- helix
- antihelix
- concha
- tragus
- antitragus
- lobule
In the average adult, how long is the external acoustic meatus?
The canal is about an inch long
What directions does the acoustic canal take?
inward –> bends backward –> bends forward and down
Where does the external acoustic meatus end?
tympanic membrane
How is the acoustic canal divided up?
- outer 1/3 is cartilaginous (secrete cerumen; wider)
- inner 2/3 is bony (NO cerumen; narrower)
Middle ear ossicles
- malleus/”hammer” (most lateral)
- incus/”anvil”
- stapes/”stirrup” (most medial)
What is the roof of the middle ear called?
tegmen tympani
What space is directly INTERNAL to tympanic membrane?
tympanic cavity
What space is directly ABOVE the tympanic membrane?
epitympanic recess
What is the tympanic membrane composed of?
- skin
- mucous membrane
- connective tissue
Which ossicle is attached to the inner side of the tympanic membrane?
malleus
Umbo
center-most depressed portion of tympanic membrane
Medial wall of middle ear
promontory created by base of the cochlea
Two openings associated with promontory
- fenestra vestibuli (oval; receives footplate of stapes)
- fenestra cochlea (round; closed by membrane)
Anterior to tympanic membrane
tympanic cavity (contains tensor tympani)
Tensor tympani has an opening leading to the…
eustachian/auditory tube
Eustachian/auditory tube
- connects middle ear and nasopharynx
- 1/3 bony (auditory end) and 2/3 cartilaginous (nasopharyngeal end)
Tubal tonsil
collection of lymphoid tissue in opening of auditory tube in nasopharynx
aditus ad antrum (opening to the mastoid antrum)
communicates below and behind tympanic membrane with the mastoid air cells
Pyramidal eminence originates with the…
stapedius muscle
The 3 ossicles are united by ________ and are suspended in air by ____________
- joints
- their attachments to each other, the tympanic membrane, and the oval window
Nerves coursing within the ear
- tympanic plexus (from tympanic branch of CN IX)
- chorda tympani branch of CH VII
Internal ear most responsible for…
essential organs for hearing and sense of balance
Organs of the internal ear
- cochlear duct (for hearing)
- semicircular ducts (for balance and position)
- utricle (for balance and position)
- saccule (for balance and position)
Organs of the internal ear contain a fluid called…
endolymph, which stimulates sensory endings, which stimulates fibers of CN VIII to fire and send info to brain
Membranous labyrinth
- composed of semicircular ducts, cochlear duct, utricle, and saccule
- contained within bony labyrinth
Bony labyrinth components
- cochlea (contains cochlear duct)
- vestibule (contains utricle and saccule)
- semicircular canals (contains semicircular ducts)
Where is perilymph found?
between the bony and membranous labyrinth
Cupula
center of cochlea
Osseous spinal lamina
along with membranous labyrinth, divides internal cochlea into
- scala vestibuli
- scala tympani
Round (cochlear) window
- allows expansion of fluid upon vibration
- covered by a membrane
- found at base of cochlea
Vestibule location
- middle portion of bony labyrinth
- relates to the cochlea lying anteriorly
- relates to semicircular canals lying posteriorly
Oval (vestibular) window
- opening in lateral vestibular wall
- accommodates the footplate of stapes
What do vibrations of the stapes produce?
surges in the fluid of the vestibule
Three semicircular canals
- anterior canal
- lateral canal
- posterior canal
Ampulla
- the enlargement where the semicircular canal joins the vestibule
- it’s through here that the fibers from the vestibular portion of CN VIII pass
What lines internal cavity of the bony labyrinth?
membranous labyrinth
Membranous labyrinth main function
convert the mechanical energy of the vibrating fluid to electrical energy that can be carried to the brain via CH VIII
What forms the membranous part of the bony trochlea?
cochlear duct
Cochlear duct is modified into…
- vestibular (Reissner’s) membrane
- basilar membrane
Basilar membrane modification
spiral organ (of Coti), sensory ending for hearing of CN VIII
What forms the membranous part of the bony vestibule?
- utricle
- saccule
Utricle and saccule each have a portion of ________, which is responsible for _________
- sensory epithelium
- communicating with vestibular portion of CN VIII for perception of static position sense
What is the membranous part of the anterior, posterior, and lateral semicircular canals?
semicircular ducts
Ampullary crest
where the fibers from the vestibular portion of CN VIII pass
