Ear

Question 1

Auricle

Answer 1

. Primarily formed the auricular cartilage
. Lobule is lower part of auricle
. Non-cartilaginous and contains fatty eraolar tissue

Question 2

External auditory meatus (EAM)

Answer 2

. Canal extending from external opening to tympanic membrane
. Cartilage forms walls of lat. 1/3rd
. Bone forms walls of med. 2/3rd
. Skin w/ hair, sebaceous glands and modified sweat glands that produce cerumen (ear wax) line the cartilaginous portion of EAM

Question 3

General sensory innervation to auricle and EAM

Answer 3

. Auriculotemporal n. To ant. Sup. Portion of auricle, EAM, and external surface of tympanic membrane
. Vagus n. To area around meatus, inf. Portion of EAM and the external surface of tympanic membrane
. Facial n. To area around meatus
. Lesser occipital n. (C2/3) to post. Sup. Auricle
. Great auricular n. (C2-3) to post. Inf. And lat. surface of auricle

Question 4

Tympanic cavity

Answer 4

. Located w/in petrous temporal bone
.houses auditory ossicles
. Lined w/ mucosa that is continuous w/ pharyngotympanic tube, mastoid air cells, and mastoid antrum

Question 5

Tympanic cavity boundaries

Answer 5

. Roof: tegmen tympani formed by petrous portion of temporal bone
. Floor: thin layer bone. Internal jugular v. Arises opposite
. Lat. wall: opening from EAM closed by tympanic membrane
. Med. wall: formed by bony labyrinth of inner ear, facial canal
. Ant. Wall: opening to pharyngotympanic tube
. Post. Wall: aditus, facial canal

Question 6

Tympanic cavity ant. Wall features

Answer 6

. Opening to pharyngotympanic tube
. Post. Lat. 1/3 of tube is bony, remainder is cartilaginous
. Tensor tympani m.: sup. Portion of only tube directly beneath the tegmen tympani, attaches to handle of malleus
. Opening of cartilaginous portion of tube in inf. Portion of bony tube
. Pharyngotympanic tube connects middle ear to nasopharynx
. Normally tube is closed but opens to allow passage and mucus into/out of tympanic cavity

Question 7

Posterior wall features

Answer 7

. Aditus: sup. Opening leading to post. Open area (mastoid antrum) that leads to mastoid air cells w/in mastoid process
. Prominence of facial canal: vertical portion of this canal courses w/in post. Wall and contains descending portion of facial n.
. Pyramidal eminence: small, bony projection that encloses stapedius m.

Question 8

Mastoiditis

Answer 8

. Infection of mastoid air cells
. Difficult to treat and have potential to spread intracranial
. Primary treatment is IV antibiotics followed by oral antibiotics
. Can require surgical drainage

Question 9

lateral wall features

Answer 9

. Tympanic membrane set in temporal bone at inner part of EAM, external surface concave
. Handle of malleus attaches to internal surface of membrane and appears as projection of membrane in external view
. Umbo: peak of depressed central area inf. To handle of malleus

Question 10

Cochlear promontory

Answer 10

. Rounded prominence on med. wall of cavity formed by outward projection of cochlea

Question 11

Tympanic plexus

Answer 11

. Branch of CN IX that courses over promontory
. After CN IX exits jugular foramen, the tympanic n. Splits off and enters tympanic cavity via tympanic canaliculus
. Tympanic n. Composed of general sensory fibers and preganglionic parasympathetic fibers branches and combines w/ postganglionic sympathetic fibers from internal carotid a. Plexus to form tympanic plexus

Question 12

Post. To promontory on the med. wall of tympanic cavity are__-

Answer 12

. Oval window: more sup. Opening, connects to vestibule of inner ear, footplate of stapes covers oral window , oval window membrane transmits vibrations from stapes to perilymph of vestibule
. Round window: more inf. Opening, connects to cochlea, round window membrane dissipates change in cochlear pressure
. Prominence of facial canal: houses the facial n. As it courses post. W/in med. wall of tympanic cavity, bone covering the nerve may be absent in this area, exposing the facial n. To mucosa of tympanic cavity

Question 13

Auditory ossicles

Answer 13

. Malleus, incus, and stapes

. Ossicles connect to one another by synovial joints and span tympanic cavity btw tympanic membrane and the oval window

Question 14

Malleus

Answer 14

. Head, neck, and handle
. Head lies in epitympanic recess and articulates w/ incus
. Neck lies against tympanic membrane and handle is embedded in tympanic membrane
. Tendon of tensor tympani m. Inserts into handle
. Chorda tympani n. Crosses btw neck of malleus and long crus of incus

Question 15

Incus

Answer 15

. Body, long crus, and short crus
. Body articulates w/ head of malleus in epitympanic recess
. Long crus articulates w/ head of stapes
. Short crus attaches via ligament to post. Wall of tympanic cavity

Question 16

Stapes

Answer 16

. Head, neck, and 2 limbs that attach to footplate
. Head of stapes articulates w/ long crus of incus
. Footplate fits into oval window

Question 17

Tensor tympani m.

Answer 17

. Courses from bony pharyngotympanic tube
. Attaches to handle of malleus
. Contraction pulls the tympanic membrane med., tensing it, and dampening effect of sound waves
. Innervated by n. To tensor tympani (CN V3)

Question 18

Stapedius OIAN

Answer 18

. O pyramidal eminence
. I: tendon to neck of stape
. A: pulls footplate away from oval window and dampens sound energy
N: motor from CN VII

Question 19

Hyperacusis

Answer 19

. Caused by axial n. Paralysis

. Moderate to extreme sensitivity to loud noises due to loss of stapedius function

Question 20

Course of facial n. Through temporal bone

Answer 20

. Enters internal acoustic meatus and bends post. At geniculum of facial n. Where geniculate ganglion is
. Courses post. W/in med. wall of tympanic cavity got short distance then descends w/in pot. Wall of tympanic cavity
. Gives off 4 branches in facial canal
. Facial n. Proper exits facial canal at sylomastoid foramen

Question 21

Branches of facial n. Branches off in facial canal

Answer 21

. Greater petrosal n.: branch at geniculate ganglion but don’t synapse, then exit tegmen tympani and course along floor of cranial cavity
. N. To stapedius
. Chorda tympani: courses ant. Btw malleus and incus and exits middle ear cavity via petrotympanic fissure
. Auricular branches

Question 22

Bony labyrinth of of inner ear

Answer 22

. Cochlea, vestibule, and semicircular canals housing membraneous labyrinth
. Cochlea coils 2.5 times, round window opens into it
. Vestibule lies btw cochlea and semicircular canals and is in communication w/ both, oval window in wall of this
. 3 semicircular canals (ant., post., lat.) are set and right angles to each other
. Lat. canals of opposite sides are horizontal in orientation
. Ant. Canal of 1 side lies in same plane as post. Canal of opposite side
. Perilymph btw wall of bony labyrinth and outer wall of membranous labyrinth

Question 23

Membranous labyrinth

Answer 23

. Inside bony labyrinth
. Cochlear duct, utricle and saccule, and 3 semicircular ducts w/ ampullae
. Semicircular ducts open into utricle
. Utricle and saccule communicate via utricosaccular duct
. Saccular continous w/ cochlear duct
. Parts of labyrinth lie btw 2 perilymph-filled chambers
. Contains endolymph that produces fluid waves in response to fluid waves produced in perilymph

Question 24

Components to hearing

Answer 24

. Mechanical translation of sound waves into sonar waves

. Translation of sonar waves into sensorineural impulses

Question 25

How vibrations get to membrane of oval window?

Answer 25

. Sound waves pass through EAM to vibrate tympanic membrane
. Vibrations pass from tympanic membrane to malleus, incus, and the stapes
. Footplate of stapes vibrates on oval window membrane

Question 26

How do vibrations go from oval window membrane to round window membrane

Answer 26

. Vibrations from oval window create sonar waves in perilymph of vestibule
. Sonar waves pass along one perilymph-filled channel to ascend to the apex of the cochlea
. Vibrations then descend via other channel and are dissipated back to tympanic cavity at membrane of round window

Question 27

How do sonar waves go from perilymph to sound

Answer 27

. Perilymph-filled chambers produce sonar waves in endolymph of cochlear duct
. Stimulate hair cells of cochlear division of CN VIII
. Hair cells generate nerve impulses that are sent to the brain and are perceived as sound
. Different regions of cochlear duct perceive different pitches

Question 28

Conductive hearing loss

Answer 28

. Damage to or loss of any structure that assists in creating movement at oval or round windows or disrupts sound transmission in outer or middle ear
. May be temporary issue
. Congenital conductive hearing loss may be due to absence or malformation of external or middle ear structures, surgical correction may be possible or hearing may be improved by amplification w/ conventional or bone conduction hearing aid

Question 29

Sensorineural hearing loss

Answer 29

. Lesion or damage to any portion of nervous system that is involved w/ conduction and interpretation of n. Impulses from vestibulocochlear n.
. Loss of components w/in cochlea causes sensorineural deafness that is frequency-specific (can’t heat specific pitches)
. Loss of hair cells will result in almost complete instability to detect specific frequencies regardless of how loud they are
. Can only be corrected w/ cochlear implant

Question 30

Translational motion

Answer 30

. Linear acceleration and tilting of head in x, y, or z direction
. Maculae: specialized areas of sensory epithelium located w/in utricle and saccule, consists of hair cell receptors and assoc. supporting cells
. Gelatinous membrane overlies haircell bundles w/ otolithic membrane embedded in otoconia above it
. Otoconia make otolithic membrane heavier than surrounding fluids so when head tilts gravity causes the membrane to shift relative to maculae that stimulates hair cell receptors

Question 31

Rotational acceleration

Answer 31

. Rotation about thee axes (roll, pitch, yaw)
. Ampullae: dilations at one end of each semicircular duct
. W/in ampullae are hair cell receptors embedded w/ gelatinous substrate
. Angular acceleration of endolymph in semicircular ducts distorts the gelatinous mass which stimulates hair cell receptors
. Semicircular canals 90 degree angles to one another in all 3 directions
. Canals of both ears act in concert to coordinate equilibrium

Question 32

Benign paroxysmal positional vertigo

Answer 32

.common cause of vertigo in people over 50
. Patients experience mild to intense dizziness following specific head positioning changes
. Otoconia becomes dislodged and settle in semicircular canals resulting in sensitivty to specific positional changes
. Epilepsy maneuver helps