Ear Flashcards
What joins the middle ear to the nasopharynx?
Auditory tube
What separates the external and middle ear?
Tympanic membrane
What is the auricle?
The part of the ear that collects sound
What is the external acoustic meatus?
Conducts sound toward the tympanic membrane
What forms the outer ear?
Auricle and external acoustic meatus
What are the structures on the auricle? (7)
Helix, antihelix, tragus, antitragus, scaphoid fossa, lobule, concha
Sensory innervation to the outer ear is by what three nerves? Where do the come from?
. Auriculotemporal nerve (V3)
. Greater auricular nerve (cervical plexus C2-C3)
. Lesser occipital nerve (cervical plexus C2-C3)
What parts of the ear do the auriulotemporal, greater auricular, and lesser occipital nerves innervate?
Auriculotemporal - anterior wall of external acoustic meautus, ~2/3 of the exterior surface of the tympanic membrane, tragus, and the ear/skin superior to the tragus
Greater auricular - lobule, most of helix/anti-helix, most of cranial surface
Lesser occipital - upper part of cranial surface
What nerves serve the concha and external acoustic meatus? Functional components?
CN VII innervates dots in the concha (SA)
The auricular branch of CN X innervates the external acoustic meatus and ~1/3 of the surface of the external tympanic membrane (SA)
Blood supply to the auricle and external acoustic meatus (2)?
Posterior auricular
Superficial temporal
Lymph drainage of the auricle and external acoustic meatus?
Superficial parotid LNs - lateral surface of superior half of auricle
Mastoid and deep cervical LNs - cranial surface of superior half
Superficial cervical LNs - remainder of auricle and lobule
What bone is the middle ear located in?
Petrous part of temporal bone
What are the contents of the middle ear?
3 auditory ossicles
Stapedius and tensor tympani muscles
Chorda tympani (CN VII)
Tympanic plexus
Innervation to the mucosa of the middle ear is from what nerve? Functional components?
CN IX (VA)
Innervation of internal surface of tympanic membrane? functional components?
CN IX (VA)
Where will you see the cone of light? What is it from?
Projecting down from the umbo (which is “attached” to the handle of the malleus)
Reflection of light from an otoscope
The chorda tympani travels _______ the incus
Behind
So it travels behind the incus and kind of crosses over the tympanic membrane
Do the auditory ossicles have periosteum?
No, but they are covered with mucosa
What does the malleus articulate with?
Tympanic membrane and incus
What does the incus articulate with?
Malleus and stapes
What does the stapes articulate with?
Incus and Oval window
Whats on the other side of the oval window?
Fluid filled chambers of cochlea
Why is the vibratory force of the stapes increased _____ times over that of the tympanic membrane?
10x
Because its smaller than the tympanic membrane
What do the auditory ossicles do?
Increase force but decrease amplitude of vibrations transmitted by the tympanic membrane
What happens when the stapes vibrates on the oval window?
Fluid current changes in the chambers of the cochlea create the specialized hair cells in the Organ of Corti to trigger impulses to the brain via CN VIII
What are the 6 walls of the middle ear cavity?
Carotid - anterior Mastoid - posterior Membranous - lateral Labyrinthine - medial Tegmental - roof Jugular - floor
What does the chorda tympani do again? Functional components?
Transmits ss-taste from the anterior 2/3 of the tongue
Carries VE-para/pre fibers to the submandibular ganglion via the lingual nerve
ss-taste, VE-para/pre, VA
What does the tensor tympani do, where is it attached, what is is innervated by?
Dampens vibration of the malleus
(head of malleus extends to the epitympanic recess)
It attaches to the handle of the malleus and cartilage of the auditory tube
Innervated by V3
What does the labyrinthine wall separate?
Middle ear from inner ear
On a bony elevation called the promontory (formed by cochlea), there is a _________ created by which nerve?
Tympanic plexus
Tympanic branch of CN IX
The tympanic plexus condenses superiorly as the _____________.
Lesser petrosal nerve
What are the functional components of lesser petrosal, and where is it going?
VE-para/pre fibers to the otic ganglion
Para/post fibers from the otic ganglion will supply which gland?
Parotid gland
What are the two windows on the labyrinthine wall, and what does each do?
Oval - foot of stapes
Round - responds to current changes created by the foot plate of the stapes on the oval window
What does the carotid wall separate?
Tympanic cavity from the carotid canal
The carotid wall is associated with what three structures?
ICA, opening of auditory tube (connects middle ear to nasopharynx), and canal for tensor tympani muscle
The auditory tube allows for what?
Pressure of middle ear and atmospheric pressure to be equalized
The posterolateral 1/3 of the auditory tube is ________ while the rest is _________.
Bony while the rest is cartilaginous
The mastoid wall has an opening that leads to what? What lines the opening?
Mastoid antrum (chamber) Mastoid air cells
The posterior also has a canal for what nerve? Whats the canal called?
Facial canal for CN VII
It travels through the canal on its way out of the skull via the stylomastoid foramen. It gives off the chorda tympani before exiting the skull.
What does the stapedius do and where is it located?
Acts to dampen the vibration of the stapes (CN VII)
Originates from small pyramidal eminence on posterior wall and attaches to stapes
The tegmental wall is composed of a thin layer of bone called the __________. What does it do?
tegmen tympani
Separates the tympanic cavity from the dura mater on the floor of the middle cranial fossa
The jugular wall is separated from what?
A layer of bone separates the tympanic cavity from the superior bulb of IJV
Which labyrinth contains endolymph? Perilymph?
Membranous labyrinth contains endolymph
Bony labyrinth contains perilymph
The membranous labyrinth is suspended within the bony labyrinth via?
Either by delicate filaments or the spiral ligament
What is peri/endolymph for?
Stimulating the end organs for balance and hearing
What is the bony labyrinth?
A series of cavities (cochlea, vestibule, and semicircular canals) contained within the otic capsule of the petrous part of the temporal bone
Is the otic capsule more or less dense than the petrous temporal bone?
More
What is the cochlea?
Portion of inner ear responsible for hearing
It is shell-shaped and contains the cochlear duct
Describe the spiral canal
The spiral canal of the cochlea begins at the vestibule and makes 2.5 turns around a bony core known as the modiolus
Modiolus?
Contains canals that allow for the passage of blood vessels and the cochlear nerve
Cochlear aqueduct?
The bony labyrinth communicates with the subarachnoid space superior to the jugular foramen through the cochlear aqueduct
What is the vestibule?
Small oval chamber that contains the utricle and saccule and parts of the vestibular labyrinth (balancing apparatus)
What is on the lateral wall of the vestibule?
The oval window
What does the vestibular aqueduct do?
Creates continuous connections between the vestibule and the cochlea anteriorly, semicircular canals posteriorly, and posterior cranial fossa.
What does the vestibular aqueduct transmit?
Endolymphatic duct and two small vessels
The semicircular canals (anterior, posterior, lateral) are _______ and set at _________ angles from each other
open, right
Each semicircular canal forms about ______ of a circle and contains a bony _________ at one end.
2/3, ampulla
How many openings do the semicircular canals have into the vestibule?
5 (anterior and posterior canals share a common limb)
The membranous labyrinth is divided into what three structures?
Vestibular labyrinth (utricle and saccule) Cochlea labyrinth (cochlear duct in cochlea) Semicircular ducts (in semicircular canals)
The semicircular ducts open up into the utricle via how many openings?
5
The utricle communicates with the saccule through what? What arises from this structure?
Utriculosaccular duct
The endolymphatic duct arises from the utriculosaccular duct.
The semicircular ducts respond to ____________ head movements
rotational (angular accelerations)
What is the ductus reunions?
The saccule is continuous with the cochlear duct through the ductus reunions
The utricle and saccule respond to __________ movement
linear
What is maculae
Specialized areas of sensory epithelium in the utricle and saccule
Each ampulla at the end of each semicircular canal contains a sensory area known as?
ampullary crest
What are sensors in the ampullary crests doing?
Recording movements of the endolymph in the ampulla resulting from rotation of the head in the plane of the duct
What does the vestibular ganglion house?
Cell bodies of neurons that are associated with hair cells of the crests and macullae
The cochlear duct is a spiral, blind tube that is ________ at one end
closed at one end
What suspends the cochlear duct across the cochlear canal?
Spiral ligament on external wall of cochlear canal
Osseous spiral lamina of the modiolus
Helicotrema?
Apex of the cochlea that provides communication between the two channels of the perilymph-filled spiral canal
The endolymph-filled cochlear duct divides these two channels
Scala vestibuli vs scala tympani
Vestibuli is in contact with the oval window
Tympani is in contact with the round window
Roof and floor of cochlear duct?
Vestibular membrane
Basilar membrane
Receptor of auditory stimulation? Where does it lay?
Organ of Corti
Between tectorial membrane and basilar membrane
What goes through the internal acoustic meatus
CN VII
CN VIII
internal auditory artery
Functional components of CN VIII?
Vestibular branch - SS fibers for equilibrium and balance
Cochlear branch - SS fibers for hearing
Otitis media
Inflammation of middle ear cavity (often secondary to upper respiratory infections)
Inflammation can cause blockage of the auditory tube
Microtia
(means small auricle)
Results from depressed development of auricular hillocks
May indicate atresia of the external acoustic meatus and an abnormal middle ear cavity
