G56: Ear Flashcards
General sensory innervation to anterior superior portion of auricle?
Auriculotemporal n
General sensory innervation to area surrounding meatus?
Facial n and Vagus n
General sensory innervation to posterior superior portion of auricle and medial surface?
Lesser Occipital n
General sensory innervation to inferior portion of auricle and lateral and medial surfaces?
Great Auricular n
Wall of lateral 1/3 EAM is composed of
cartilage (skin containing hair, sebaceous glands and modified sweat glands (cerumen))
Wall of medial 2/3 EAM is composed of
bone
EAM curves
convex superior and posteriorly
General sensory innervation to superior EAM and external surface of tympanic membrane?
Auriculotemporal n.
General sensory innervation to inferior EAM and external surface of tympanic membrane?
Facial n and Vagus n
Tympanic cavity
petrous portion of temporal bone, sound waves converted to motion
Tympanic cavity is connected anteromedially with
nasopharynx via the auditory tube
Tympanic cavity is connected posteromedially with
mastoid antrum
Lining of the tympanic cavity
mucous membranes continuous with auditory tube, mastoid air cells, and mastoid antrum
If the tympanic cavity is a room with 4 walls, the roof would be?
Tegmen tympani, the petrous portion of the temporal bone, forming the floor of the middle cranial fossa;
If the tympanic cavity is a room with 4 walls,the floor would be?
Jugular wall, the thin wall of the jugular foramen
If the tympanic cavity is a room with 4 walls, the lateral wall would be?
Tympanic membrane
If the tympanic cavity is a room with 4 walls, the medial wall would be?
Bony Labyrinth housing the inner ear
If the tympanic cavity is a room with 4 walls, the anterior wall would be?
opening of the bony portion of the auditory tube
If the tympanic cavity is a room with 4 walls, posterior wall would be?
Aditus leading to the mastoid antrum
Epitympanic recess
is a expanded area of the tegmen tympani that houses the malleus and incus bones
Cochlear promontory
rounded hollow prominence on the medial wall of the cavity, formed by the outward projection of the cochlea
Tympanic plexus (CN9)
courses of the promontory
CN9 exits the jugular foramen and a branch, tympanic nerve enters
tympanic canaliculus (sensory and pregang), innervates the tympanic cavity, auditory tube, and mastoid air cells, and forms the lesser petrosal n
The lesser petrosal n exits the tympanic cavity via
through the tegmen tympani and runs through the lesser petrosal canal
What’s located posterior and superior to the promontory on the medial wall of the tympanic cavity?
Oval window and the canal for the facial n
Oval window
the opening into the vestibule of the inner ear, covered by footplate of the stapes
Canal for facial n
enters IAM to stylomastoid foramen, in IAM theres the geniculate ganglion (it is here that pregangs form the greater petrosal n)
Auditory tube in the anterior wall splits into
superior and inferior portions; connects middle ear and nasopharynx
Superior portion of the auditory tube
contains tensor tympany muscle, which attahces to the handle (manubrium) or the malleus
Inferior portion of the auditory tube
contains the opening of the crtilaginous portion of the tube
Tensor tympani and cartilaginous portion run
parallel to each other
Aditus in posterior wall
leads to an open area called mastoid antrum leading to mastoid air cells
Inferior to the aditus is
the facial canal containing the descending portion of the facial n. here the n splits into 4 branches (greater petrosal, n to stapedius, chorda tympani, auricular) and the pyramidal eminence
Pyramidal eminence
small bony projection enclosing the stempedius m
Otitis media
middle ear infection, red bulging tympanic membrane
Umbo
at the peak of the depressed tympanic membrane area (inferior to the attachment of the handle of the malleus)
Handle of malleus
attached to the tympanic membrane
Cone of light
radiating from the inferior portion of th ehandle of malleus
Pars flaccida
relaxed superior portion of the membrane (chorda tympani crosses here)
Pars Tensa
inferior portion of the membrane
Innervation of the external surface of the tympanic membrane
auriculotemporal, vagus, facial
Innervation of the medial surface of the tympanic membrane
glossopharyngeal n.
Ossicles
malleus, incus, and stapes connected by synovial joints
Malleus
Head: lies in epitympanic membrane articulates with incus
Neck and handle: lies against and embedded in tympanic membane
tendon of tensor tympani (sup div of auditory tube) inserts
on the handle of the malleus
Chorda tympani crosses the
medial surface (pars flaccida) of the tympanic membrane
Incus
body, long crus, and short crus
Incus head
articulates with head of malleus in epitympanic recess
Incus long crus
inferior portion articulates with the stapes
Incus short crus
attaches to a ligament attached to the posterior wall of the tympanic cavity
Stapes
Head, short neck, two limbs, footplate
Head of stapes
articulates with the long crus of incus
Stapes footplate
fits in the oval window
Malleus and incus and incus and stapes joints
SYNOVIAL joints
Vibrations of the tympanic membrane
move ossicles transmitted to oval window via the footplates of the stapes
Tensor tympani m
auditory tube to handle of malleus, pulls tympanic membrane medially, dampening the effects of sounds waves (n. to tensor tympani V-3)
Stapedius m.
bony pyramid on posterior wall and attaches vis tendon to neck of stapes; pulls footplate away from oval window, dampening the sound; (innervated by CN7)
Hyperacusis
paralysis of CN7 (Bell’s palsy) can cause sensitivity to loudness due to function loss of stapedius
Inner ear
bony labrinth and membranous labrinth
Bony labrinth houses
membranous labrinth and perilymph is located between, endolymph is contained within membranous labrinth
Bony Labrinth consists of
cochlea, vestibule, and semicircular canals
Cochlea
2.5X spins, perilymph wave through cochlea in response to movement of oval window (round window opens)
Vestibule
area between cochlea and semicircular canal (oval window is in wall of vestibule)
Semicircular canals
Anterior, Posterior, and Lateral at right angles (x, y, z axis) lateral canal are horizontal and anterior canal and posterior canal are in same plane of opposite sides
Membranous labrinth
Cochlear duct, utricle, saccule, and semicircular ducts
Hearing:
fluid waves in endolymph of cochlear duct stimulate receptor cells and mechanical movement is conducted into nerve impulses
Equilibrium
angular acceleration of endolymph in vestibular ducts stimulates receptors, each side work in concert
Maculae
specialized area of sensory epithelium within the utricle and saccule; monitor head position
semicircular ducts open into
utricle
utricle and saccule communicate via
utricosaccular duct
Saccule is continuous with
cochlear duct
Innervation of the ear
CN8, cochlear division and vestibular division
Conductive hearing loss
loss of any structure that assists in creating movement at the oval and round windows
Sensorineural hearing loss
lesion or damage of any portion of the nervous system involved in conduction or interpretation of nerve impulses