14-Anatomy of the Ear brainscape

Question 1

Benign Paroxysmal Positional Vertigo

Answer 1

otoliths from utricle or saccule become disloged and mgirate into one of the semicircular canals *Leads to short intense dizzy spells usually after head movement *Can use a Canalith repositioning procedure in different head positions to get them back into place

Question 2

Boundaries of the Middle Ear (Tympanic) Cavity & key anatomical points

Answer 2

Roof: Tegmen tympani (petrous part of temporal bone) Floor: Jugular fossa (separation from internal jugular vein)- tympanic branch of CN IX enters middle ear here Lateral (membranous): tympanic membrane Medial (labyrinthine) lateral wall ofthe inner ear, oval and round windows Posterior (Mastoid): mastoid air cells, associates with pyrimidal eminence (where stapedius tendon enters middle ear) and where chorda tympani enters Anterior: thin bone on lower part, superiorly large opening for eustachian tube, small opening for the tensor tympani muscle, and foramen for exit of chorda tympani

Question 3

Ceruminous glands

Answer 3

in the cartilaginous portion fo the external auditory meatus- produce earwax

Question 4

Cholesteatoma

Answer 4

benign tumor of skin that penetrates TM into middle ear space- can lead to bone loss there

Question 5

Cochlear Implant

Answer 5

*electrodes introduced into the cochlea, connected to sound processor and microphone if the auditory nerve suvives

Question 6

Components of hte Middle Ear

Answer 6

*Tympanic cavity *Auditory ossicles (malleus, incus, stapes) *Stapedius & tensor tympani muscles *Communicates with the nasopharynx via eustachian tube

Question 7

Components of the Bony Labyrinth

Answer 7

*Vestibule (between the next two) *Three semicircular canals *Cochlea Contains perilymph, in which the membranous labyrinth is suspended

Question 8

Components of the Inner Ear

Answer 8

Bony Labyrinth Membranous Labyrinth - utricle, ssaccule, semicircular ducts, cochlear duct, *Acoustic & vestibular ganglion

Question 9

Components of the Membranous Labyrinth

Answer 9

Utricle Saccule Semicircular ducts Cochlear Duct (organ of corti) *All are suspended in perilymph, and contain endolymph

Question 10

Crista ampularis

Answer 10

Region where the hair cells of the semicircular canal are located

Question 11

Describe the course of the facial nerve from the internal acoustic meatus to the stylomastoid foramen

Answer 11

1) Facial nerve enters internal acoustic meatus 2) At distal end of the IAM it enters the facial canal and continues between internal and middle ears 3) Enlarges to form the sensory geniculate ganglion and gives off the greater petrosal nerve 3) Turns sharply downward, gives a nerve to the stapedius, gives off the chorda tympanii, then exits skull almost vertically through the stylomastoid foramen

Question 12

Difference in concentrations in endolymph and perilymph

Answer 12

Endolymph: HIGH concentration of K+ and Ca2+ Perilymph: low concentration of K+ and Ca2+

Question 13

External Ear Components

Answer 13

*Auricle *External acoustic meatus

Question 14

Function of cochlea

Answer 14

Perceives sound

Question 15

Function of the external, middle, and internal segments of the ear

Answer 15

External: Captures sound Middle: Transmits vibrations of tympanic membrane across cavity to the internal ear via the middle ear bones Internal: Convert mechanical movement to electrochemical in the spiral organ to transmit along CN VIII

Question 16

Function of the Saccular and Utricular Regions

Answer 16

aka macula- perceive linear acceleration/deceleration & gravity

Question 17

Function of the semicircular canals

Answer 17

perceive rotational movements & related head movements

Question 18

Hair cells in the Cochlea (organ of corti)

Answer 18

Inner & Outer Cells: Inner: only one row, Type I hair cells Outer: three rows of bundles, Type II hair cells no kinocilium, has a cupula membrane instead of the otolithic membrane that was in the utricle and saccular sections *Auditory of CN VIII enters cochea and synapses here

Question 19

Hearing Aids

Answer 19

generally (analog) or selectively (digital) amplify sounds coming into the ear *Digital= can shift incoming freqeuncies to cochlear regions that retain hearing

Question 20

How can mechanosensory hair be lost?

Answer 20

as a result of genetic mutations, or acute or chronic exposure to loud noises

Question 21

How do mechanosensory hair cells assist in sound transduction?

Answer 21

They are epithelial cells with a stereociliary bundle on their apical surface and kinocilium adjacent to the bundle. Transmit afferent signals to brain via CN VIII 1) Stereoceilia moves toward kinocilium –> ion channels open, influx of K+ –> Depolarization –> Afferent nerve impulse 2) Stereocilia move away from kinocilium –> ion channels are shut, there is hyperpolarization –> no impulse

Question 22

Mechanosensory hair cells of the Utricle & Saccule

Answer 22

Arranged in plane, connected by Tip links, and have an Otolithic membrane that contains otoliths on top of it for added weight

Question 23

Meniere’s Disease

Answer 23

persistent dizziness & nausea (vertigo & tinnitus) from endolymphatic hydrops (increased endolymph) which leads to a rupture of the membranes separating the endolymph and perilymph

Question 24

Movement of Sound waves

Answer 24

1) Enter through oval window 2) Travel up cochlea through the scala vestibuli 3) Pass through the scala media –> can induce movement of tectorial memrbane, and therefore induce the movement of hair cells 4) Travels down cochlea through scala tympani 5) Exit cochlea through round window

Question 25

Otitis Externa

Answer 25

infection of outer ear- can be seen at the Tympanic membrane

Question 26

Otitis Media

Answer 26

bacterial infection of midle ear that usually moves from the auditory tube *Most common reason why children <5 are taken to physician

Question 27

Otosclerosis

Answer 27

overgrowth of middle ear ossicles, usually affects the stapes *Fixation of middle ear ossicles –> can lead to mild to severe hearing loss *Also if they are too big they can impinge on the facial nerve because it runs underneath the bones *Can be fixed with prosthetic if necessary

Question 28

Otoscopic appearance of a normal tympanic membrane

Answer 28

*Should be relatively translucent, with reddish tinge. Malleus should be visual and cone of light should be seen *it is connected to the malleus, and the chorda tympani will be more medial than the TM

Question 29

Oval Window

Answer 29

point of attachment for the base of the stapes, communicates middle ear with the bony labyrinth (inner ear)

Question 30

Pillar Cells

Answer 30

supporting cells in the organ of corti that form a tunnel between the inner and outer hair cells of the cochlea

Question 31

Round Membrane

Answer 31

moves in opposite way of the oval window in order to reduce the pressure that is induced by endolymph waves in the cochlea

Question 32

Sesnsory Innervation of the Auricle/Pinna

Answer 32

More superficial = Lesser Occipital and greater auricular (from cervical plexus) and the auriculotemporal branch of V3 *Deeper= Facial (VII) and Vagus (X)

Question 33

Spaces of the Cochlea

Answer 33

1) Scala tympani (filled with perilymph_ 2) Cochlear duct (aka scala media) 3) Scala vestibuli (filled with perilymph)

Question 34

Types of Hair Cells in the Ear

Answer 34

Type 1: Round, surrounded by nerve calyx made up of large afferent nerve ending that increases their innervation Type 2: Ovular, does not have nerve calyx, less heavily innervated

Question 35

Waardenburgs Syndrom

Answer 35

autosomal dominant type of congenital deafness associated with pigment abnormalities

Question 36

What is the clinical significance of an association between the nasopharynx and the mastoid air cells?

Answer 36

an infection can spread up the pharyngotympanic tube, infect the middle ear, and then spread up tho the mastoid air cells

Question 37

Where are hair cells in the cochlea located

Answer 37

Cochlear duct, embedded within the tectorial membrane

Question 38

Where is endolymph produced?

Answer 38

Stria vascularis of the cochelar duct

Question 39

Where is the organ of corti?

Answer 39

In the scala media (cochlear duct) of the cochlea