Auditory Portion Of The Ear

Front 1

What is the definition of sound?

Back 1

propagated vibratory energy

Front 2

What is hearing?

Back 2

The brain's perception of sound - vibratory energy must be changed into nerve impulses

Front 3

How can sound be measured objectively and physically?

Back 3

frequency, intensity, and duration

Front 4

Frequency

Back 4

number of vibrations per second (measured in Hz)

perceived as pitch

Front 5

Intensity

Back 5

amplitude of vibrations (measured in dB)

perceived as loudness

Front 6

Duration

Back 6

temporal pattern of sounds (measured in seconds, or fractions of seconds)

perceived as temporal patterns

Front 7

What is the external ear composed of?

Back 7

the pinna, and the external auditory meatus (or ear canal)

Front 8

What is the Pinna composed of?

Back 8

elastic cartilage of irregular contours overlaid by skin - causes high frequencies of sound to reflect differentially into the external auditory meatus

Front 9

What is the function of the Pinna?

Back 9

-hold hearing aid or pencils or glasses
-earmold
-ID congenital malformations
-cosmetic - earrings
-collect sound waves and enhance high frequencies
-localize sound
*-protect by deflecting wind and debris

Front 10

What is the structure of the External Auditory Meatus?

Back 10

-air filled
-humid (about 98.6 degrees): protects Tympanic Membrane, but medium for bacteria or fungus
-irregular lazy "S" shape
-diameter of .7cm
-length of 25 mm (about 1 inch by 1/4 inch): runs from base of pinna to the tympanic membrane
-model

Front 11

What is the External Auditory Meatus composed of?

Back 11

outer portions - cartilaginous external auditory meatus
inner portions closer to the tympanic membrane - bony external auditory meatus

Front 12

What happens in the bony external auditory meatus to protect the middle ear?

Back 12

The skin adheres tightly to the bone, so that hard objects in the meatus will press the skin directly against the bone and stimulate pain fibers

keeps foreign objects out of ear

Front 13

What does the skin of the External Auditory Meatus contain?

Back 13

Hairs and 2 types of glands: 1. sabaceous glands, similar to sweat glands produce a watery solution; and 2. cerumen glands, produces a fatty solution

Front 14

What is cerumen?

Back 14

Otherwise known as ear wax, it's a sticky substance formed by the mixture of the 2 solutions

Function:
-helps keep foreign objects away from delicate Tympanic Membrane, along with hairs
-lubricates and moisturizes
-catches insects
-acidity decreases bacteria

Front 15

What is the resonant frequency of the human EAM?

Back 15

Between 3000 and 4000 Hz (more intense as it courses through the canal to the tympanic membrane)

Front 16

How much more intense is the resonant frequency of sound at the tympanic membrane?

Back 16

12 dB more intense at the TM than at the base of the Pinna

Front 17

What is the 4K notch?

Back 17

what the initial loss for noise-induced hearing loss is called, since it is measured at 4KHz (4000Hz)

Front 18

What is the function of the outer ear?

Back 18

1. Facilitates vertical localization
2. Protects middle ear apparatus
3. Increases sound intensity by about 12dB at resonant frequency of external auditory meatus

Front 19

What is the function of the External Auditory Meatus?

Back 19

-protects Tympanic Membrane from foreign objects
-keeps temperature constant
-acts as a resonator (has a resonant frequency)

Front 20

What are the clinical applications for the External Auditory Meatus?

Back 20

-atresia: malformation of the ear
-Hearing Aid molds
-Insert phones and ear plugs
-Immittance - clinical test
-Otoscopy
-Pathologies

Front 21

What is the primary function of the middle ear?

Back 21

It is an acoustical transformer that changes the air-borne vibrations that move the tympanic membrane into fluid vibrations in the cochlea

Front 22

What are the 2 major and 2 minor air spaces of the middle ear that make up the middle ear cavity?

Back 22

1. Middle Ear Proper: a.Major: Tympanum - ear cavity nearest the tympanic membrane
b. Minor: i. Mesotympanum - portion directly opposite the tympanic membrane; ii. hypotympanum - that extending below tympanic membrane; and epitympanum (attic) - above the tympanic membrane

2. i. major: Antrum - a large air space within the mastoid portion of the temporal bone; and ii. minor: Aditus ad antrum - short tunnel that connects the epitympanum with the antrum

Front 23

What are the 3 layers of the Tympanic Membrane?

Back 23

1. outer layer - thin skin continuous with the external auditory meatus
2. middle layer - radially and concentrically arranged connective tissue fibers
3. inner layer - single layer of cells continuous with lining of middle ear cavity

Front 24

What is the structure of the tympanic membrane?

Back 24

-shaped like a blunt cone, with apex (umbo) extending toward middle ear space
-Pars tensa: larger, stiff structure
-Pars flaccida or Shrapnel's membrane: superior quadrant that has little connective tissue and is less stiff

Front 25

What is the annulus?

Back 25

fibrocartilaginous ring that helps hold the tympanic membrane in place; snaps into a groove in the ossified ear canal to hold it in place

Front 26

What is the Tympanic Sulcus?

Back 26

a groove in the bony wall of EAM where the annulus snaps into

Front 27

What are the 2 divisions of the Tympanic Membrane?

Back 27

1. Pars Flaccida:
-Shrapnell's membrane: superior margin, not in sulcus, no radial fibers
-Anterior and Posterior Malleolar Folds: ligament bands from notch of rivinus to malleus
-Chorda Tympani: branch NVI- controls taste in the anterior 2/3 of the tongue

2. Pars Tensa
-rest of TM under tension because of the radial fibers

Front 28

What are the landmarks of the Tympanic Membrane?

Back 28

-color: pearly grayish white, semitransparent
-Malleolar Stria (whitish streak in membrane): manubrium of malleus
-Politzer's Cone: cone of light/light reflex in the anterior inferior quadrant (no light reflex = sign of pathology in ME)
-Chorda Tympani

Front 29

What are the functions of the Tympanic Membrane?

Back 29

1. To transform pressure changes into mechanical vibrations - since the TM is very sensitive, and highly damped (no echoes)
2. protect contents of ME

Front 30

What are the 3 ossicular bones?

Back 30

1. Malleus
2. Incus
3. Stapes

Front 31

What are the parts of the Malleus?

Back 31

*largest bone: 8-9 mm

1. head (sits in epitympanum)
2. anterior process
3. lateral process
4. manubrium: long process embedded in fibrous TM layers

Front 32

What are the 3 ligaments of the malleus?

Back 32

1. Superior - head to the roof of attic
2. Anterior - anterior process to anterior wall of ME
3. lateral - neck to notch of Rivinus

Front 33

What is the main muscle of the malleus?

Back 33

Tensor Tympani - tendon from the anterior wall (above epitympanum) to manumbrium

Front 34

What are the parts of the Incus?

Back 34

1. Body - bulk in attic; articular facet anterior
2. Short crus - posterior (root of tooth) in fossa incudis
3. Long crus - parallel to manubrium, bends medially
4. Lenticular process - ball at end of long crus

Front 35

What are the 2 ligaments of the incus?

Back 35

1. posterior - short process to fossa incudis
2. superior - to roof

Front 36

What are the parts of the Stapes?

Back 36

1. Footplate - attaches to the oval window via annular ligament
2. Posterior crus - more curved
3. Anterior crus
4. head- attached to lenticular process

Front 37

What is the ligament of the stapes?

Back 37

Annular ligament - elastic more pronounced posterior so footplate held more rigidly from behind

Front 38

What are the windows of the middle ear?

Back 38

oval window - in the superior to the medial wall where the stapes sits

round window - inferior to the medial wall, covered by a thin, but tough elastic membrane

Front 39

What is the medial wall?

Back 39

a protrusion of bone called the promontory which is caused by the basal turn of the cochlea

Front 40

What are the muscles of the middle ear?

Back 40

1. Stapedius muscle - on the posterior wall of the ME; the tendon attaches at the posterior neck of the stapes

2. Tensor Tympani - tendon comes from another wall to attach to the upper part of the manubrium

Front 41

What are the actions of the ME muscles?

Back 41

Tensor Tympani: draws malleus medially and anteriorly; contraction stiffens the TM so more sound will bounce off - protection of the inner ear

Stapedius: draws stapes posteriorly to limit movment

Front 42

What cranial nerves innervate the ME muscles?

Back 42

Tensor Tympani: NV - Trigeminal

Stapedius: NVII - facial

Front 43

What is the function of the ME muscles?

Back 43

-suspend ossicular chain between ligaments and muscles and give resilience
-to protect the inner ear from high intensity sounds by way of acoustic reflex

Front 44

What does the acoustic reflex do?

Back 44

-elicited by intensities of 80-90dB SPL or 60-100 dB SL
-the effect is a cut in the lower frequencies 40 dB at 100 Hz dropping to 0 dB above 1000

-in other words, AR cuts low frequency sounds when these muscles contract (environmental noise)

Front 45

What are the 4 parts of the Eustachian tube?

Back 45

1. osseous
2. isthmus
3. cartilaginous
4. membranous

Front 46

What is the Torus Tubarius?

Back 46

the membranous tissue at the end of the eustachian tube

Front 47

Is the Eustachian tube normally open or closed? How does it open?

Back 47

It is normally closed; but it opens by way of the:
-salpingopalatine
-levator and *tensor veli palatini
-salapingopharyngeous

Front 48

How big is the Eustachian tube in adults and in children?

Back 48

Adults: 35-38mm length
Children: 1/2 length, not osseous, horizontal - more prone to ear infections

Front 49

Where do the Eustachian tubes run?

Back 49

inferior, anterior, medially at about 45 degrees

Front 50

What are the functions of the Eustachian tubes?

Back 50

1. ventilate the middle ear space (main purpose*)
2. drainage - but doesn't empty completely
3. efficient vibration at various pressures - different air pressures inside than outside so when the air pressure changes, the middle ear needs to equalize, and the ET open to let air out

Front 51

What are the functions of the Middle Ear?

Back 51

1. protect the contents of the inner ear
2. conduct sound to the inner ear - steps up sound to get wave into motion
3. impedence matching device (transformer) - it takes more energy to move fluid than air, so there has to be more intensity to move sound through the oval window

Front 52

What are the 2 transformer methods?

Back 52

1. Lever Mechanism
-ossicles act as a lever: small force at one end moves through larger area to apply greater force
-effect about 1.3-2.5x what it was
-manubrium of the malleus and long process of the incus lie roughly parallel to one another, with the manubrium being longer than the incus

2. Area Transformation
-TM is 25 times larger than OW
-17:1 increase -- pressure on TM funneled down and placed on little oval window so the pressure is much higher since its focused in such a small area

Front 53

What is the combined effect of the area mechanism and the lever mechanism?

Back 53

about a 30 dB gain

Front 54

What effects the efficiency of the tympano-ossicular system?

Back 54

it's mass and stiffness:

-if ossicles and TM has large mass and little stiffness, it makes transmitting low friequencies easier
-if TM has small mass and great stiffness, its easier to transmit high frequencies

Front 55

What is the resonant frequency of the human tympano-ossicular system?

Back 55

Between 3-4 kHz (same as EAM)

Front 56

What happens when the stapedius contracts?

Back 56

It stiffens the ossicular chain which reduces the transmission of low frequencies

Front 57

What is the function of the anterior ligament of the malleus?

Back 57

ligament attached to the anterior process that holds the ossicle in the middle ear cavity

Front 58

What is the hole between the 2 crura of the stapes called?

Back 58

The obturator foramen

Front 59

What holds the stapes in the oval window of the middle ear?

Back 59

The annular ligament

Front 60

What are the 2 short ligaments that suspend the ossicles within the tympanum?

Back 60

1. Anterior ligament of the malleus
2. Posterior ligament of the Incus - holds the short process of the incus to the posterior wall of the tympanum near the aditus ad antrum

Front 61

What are the 3 true ligaments of the middle ear?

Back 61

1. Anterior Ligament of the malleus
2. Posterior Ligament of the incus
3. Annular ligament of the stapes

Front 62

What is the importance of the manubrium of the malleus being imbedded in the tympanic membrane?

Back 62

when the tympanic membrane vibrates, it sets the whole ossicular chain into vibration around the axis of rotation - form vibrations at the TM into piston-like vibrations where stapes fits into the OW

-ultimately cause perturbations in the cochlear fluids

Front 63

What are the 2 reflexes involving the stapedius?

Back 63

1. Stapedius Reflex - contracts in response to loud sound to help protect the inner ear from gradually intensifying sounds (test=tympanometry)

2. Vocalizations - the stapedius contracts just before vocalization and relaxes when vocalization is completed; protects our ears from being overstimulated when we speak

Front 64

What are the 3 fluid-filled columns within the cochlea?

Back 64

1. Scala Tympani - filled with perilymph
2. Scala media (or cochlear duct)- filled with endolymph
3. Scala Vestibuli - continuous with the vestibule and filled with perilymph

Front 65

What is the modiolus?

Back 65

the bony, hollow core of the cochlea that contains the cochlea division of the VIIIth cranial nerve and the bipolar cell bodies of its neurons which form the spiral ganglion

Front 66

What is the Helicotrema?

Back 66

opening at the apex of the cochlea, through which the scala tympani and scala vestibuli are continous

Front 67

where does the basal end of he scala tympani end?

Back 67

at the round window - separates the perilymph from the air of the middle ear cavity

Front 68

What is the Reissner's Membrane?

Back 68

(also called the vestibular membrane) - separates the scala media from the scala vestibuli

-very thin and composed of flat cells

Front 69

What is the basilar membrane?

Back 69

-separates the scala media from the scala tympani
-layer of radially oriented connective tissue figers
-scala media side is the organ of Corti

Front 70

What is the importance of the scala media?

Back 70

(also called the cochlear duct) - lined by epithelial cells that join one another forming a barrier through whcih extracellular fluid cannot pass, keeping the endolymph and perilymph separate

Front 71

What are the 3 areas of fibrous connective tissues within the inner ear?

Back 71

1. Spiral Limbus
2. Spiral Ligament
3. Basilar membrane

Front 72

Spiral limbus

Back 72

ridge of fibrous connective tissue lying on Scala Vestibuli surface of the osseous spiral lamina

Front 73

spiral ligament

Back 73

area of fibrous connective tissue against the outer bony wall of the cochlea turns

Front 74

Basilar membrane

Back 74

radially arranged fibers that extend from the free edge of the osseous spiral lamina to the part of the spiral ligament that is at the level of the interface between the scala tympani and the cochlear duct
-extends through coiled length of scala media, where the Organ of Corti lies
-on the scala tympani side is the perilymph

Front 75

What are the cells of the Reissner's membrane called?

Back 75

squamus cells - flat

Front 76

What happens when the Reissner's membrane reaches the spiral ligament?

Back 76

the epithelium changes and becomes a structure called the stria vascularis - 3 cell layers thick and containing numerous blood capillaries

Front 77

Spiral prominence

Back 77

just toward the basilar membrane from stria vascularis - outpocketing of cells bulging into the scala media

Front 78

Outer Spiral Sulcus cells

Back 78

single layer of low cuboidal cells that extend from the spiral prominence to the organ of Corti

Front 79

What is the Organ of Corti?

Back 79

Sensory epithelium of hearing that mostly lies on the scala media surface of the basilar membrane

Front 80

Inner spiral sulcus cells

Back 80

a single layer of cuboidal cells at the modiolar end of the basilar membrane - continuous with the peithelium along the edge of the spiral limbus

Front 81

Tectorial membrane

Back 81

a gelatinous acellular membrane comparable to the cupula of a crista ampullaris attaches to the endolymphatic surface of the interdentate cells

-tips of longest sterocilia of outer hair cells are attached to its undersurface

-no contact with inner hair cells

Front 82

Inner supporting cells

Back 82

(of the Organ of Corti) - single row that individually lie on the osseous spiral lamina, not on the basilar membrane

-each supports a single inner hair cell

Front 83

inner hair cell

Back 83

flask-shaped; morphologically similar to vestibular hair cells except for the cilia

-each have numberous stereocilia arranged in 3 or 4 rows that form shallow arc

Front 84

stereocilia

Back 84

all have rootlets in cuticular plate and extend into endolymph below tectorial membrane called the subtectorial space

-each have kinocilium that is lost during maturation

Front 85

inner and outer pillar cells

Back 85

two rows just beyond the inner supporting cells, between which is the tunnel of corti

-strong cytoskeleton that gives structural support to Organ of Corti

Front 86

Deiters' Cells

Back 86

outer supporting hair cells just beyond the outer pillar cells, each of which have a cup-shaped depression hat supports the base of an outer hair cell

Front 87

What forms the reticular lamina?

Back 87

the endolymphatic surfaces of the inner supporting cells, inner hair cells, pillar cells, Deiters' cells, and outer hair cells

Front 88

Outer hair cells

Back 88

-cylindrical in shape
-held in place at their endolymphatic "top" and at their base
-surrounded by extracellular space calle dthe Space of Nuel which is continuous with the tunnel of Corti and contains perilymph
-lack kinocilia
-rows form a W-shape

Front 89

What are the 3 types of Border cells?

Back 89

1. Hensen's cells - tallest border cells adjacent to Deiters' cells
2. Claudius' cells - shorter than Hensen's cells and lie between them and outer spiral sulcus cells
3. Boettcher's cells - found only in the basal turns

Front 90

What is the main function of the cochlea?

Back 90

it is an acoustical transducer that changes fluid vibrations into nerve impulses

Front 91

How does the cochlea transform fluid vibrations into nerve impulses?

Back 91

1. mechanical transmission of sound from stapes to a specific place alone the cochlear duct

2. amplification of the vibrations at the most excited portion of cochlear duct

3. transduction of mechanical vibrations into nerve impulses

Front 92

What is the structure of the basilar membrane and how does that influence the transmission of sound?

Back 92

the basilar membrane is narrowest and stiffest at the base of the cochlea and becomes increasingly wider and less stiff toward the apex; this stiffness gradient determines how sound is transmitted to the appropriate place along the cochlear duct

Front 93

What kind of sounds pass through the cochlear duct at its base?

Back 93

energy from 20,000 Hz sounds travel all the way to the apex before it can pass through the duct in places in between

Front 94

What kind of sounds pass through the helicotrema into the scala tympani without moving the basilar membrane?

Back 94

energy from sounds below 20Hz - basilar membrane is too stiff to respond to such low frequencies

Front 95

What does it mean to say that hair cells of the cochlea and neurons of the VIIIth nerve are sharply tuned?

Back 95

they respond with great sensitivity to a "best frequency" and poorly to higher or lower frequencies

Front 96

How are the stereocilia on the outer hair cells tonotopically arranged?

Back 96

shortest at the base - tuned to high frequencies

longest at the apex - tuned to low frequencies

Front 97

What happens when the outer hair cells move?

Back 97

they vibrate at the resonant frequency and greatly amplify the movement of the basilar membrane at that point

*process sharply tunes the cochlea

Front 98

What happens when the basilar membrane and tectorial membrane move up and down?

Back 98

causes sterocilia to bend which produces eddies in the endolymph which bend sterocilia of inner hair cells which mark the final mechanical event in cochlear excitation and the point where transduction of mechanical vibration into nerve impulses begins

Front 99

What happens when the stereocilia bend?

Back 99

it opens up the ion channels at the tips of the stereocilia of cochlear hair cells which coauses potassium ions to flow from the endolymph through the sterocilia into the hair cells

Front 100

What are the 2 labyrinths of the inner ear?

Back 100

1. Osseous labyrinth - bony case that holds sensory organs

2. membranous labyrinth - membrane that holds fluid in which rest the sensory end organs

Front 101

What are the 3 divisions of the Osseous Labyrinth?

Back 101

1. Vestibule - medial to oval window that houses the otolith organs
2. Semicircular Canals
3. Cochlea

Front 102

How many turns does the cochlea make?

Back 102

2 and 3/4 turns

Front 103

What are the 3 divisions of the Membranous Labyrinth?

Back 103

Same 3 divisions:
1. Semicircular canals
2. Otolith Organs: utricle and saccule in vestibule
3. Ductus Reuniens (duct of Hensen) - joins cochlea and saccule, connecting vestibular and auditory systems

Front 104

What are the 2 ducts of the membranous labyrinth?

Back 104

1. Endolymphatic duct - goes through hole in bone to endolymphatic sac; passes through the vestibular aqueduct and enlarges to a pouch sittin gin dura matter (endolymphatic sac)

2. cochlear duct (scala media)

Front 105

Stria vascularis

Back 105

part of the cochlea - inside the spiral ligament that offers nutrition and blood supply

Front 106

What makes up the spiral lamina?

Back 106

1. goes from modiolar wall to basilar membrane
2. terminates in hamulus (hook), making helicotrema
3. habenula perforata - opening for NVIII fibers to exit

Front 107

What are the 3 support cells on the outer wall?

Back 107

1. Claudius Cells - spiral ligamen to hensen; columnal in several rows

2. Hensen's Cells - lateral to OHC and medial to Claudius; tall support; several rows

3. Dieter's Cells - support OHC; called outer phlangeal cells

Front 108

Dieter's cells OR Phalangeal cells (inner and outer)

Back 108

support hair cells (outer aka Dieters)
body to reticular lamina process = rigid extension to top of hair cells (& control to reticular lamina)
-hold IHC very firmly

Front 109

Inner hair cells: structure and number

Back 109

-1 row lined up
-approximately 3500
-rounded base
-U shaped
-50 stereocilia

Front 110

Inner hair cells: afferent or efferent

Back 110

-afferent fibers (carry to brain): 95% connected to IHC
-twenty neurons innervated to one IHC

Front 111

Outer hair cells: structure and number

Back 111

-3 rows
-approximately 12 to 20,000
-test tube shaped
-40 to 150 stereocilia
-some longer than others
-in v and w shaped pattern

Front 112

Outer hair cells: afferent or efferent

Back 112

-efferent fibers (info carried from brain): 95% connected to OHC

Front 113

What is the function of inner ear fluids (perilymph and endolymph)

Back 113

-nutrition
-chemical energy
-medium to convey sound
-protection: contents of scala media

Front 114

Cortilymph (3rd fluid)

Back 114

-fills Tunnel of Corti
-Na+ like perilymph, but perilymph is toxic to hair cells

Front 115

What would happen if Reissner's Membrane ruptures?

Back 115

the fluid would mix and there would be no charge (dead battery)

Front 116

how does the NVIII enter the Organ of Corti?

Back 116

Through small openings in spiral lamina called habinula perforata, and terminate on hair cells

Front 117

What is the Traveling Wave Theory?

Back 117

-motion is complex
-envelope simplifies
-sharper responses at base than at apex (high frequencies vs. low frequencies)

Front 118

Outer Hair Cell electromotility

Back 118

-OHCs move at low intensities: cell itself is in a position of rest but when a sound hits it, the hair cells jump and lift basilar membrane higher than it would move on its own - narrow peak response

Front 119

Inner hair cells vs. outer hair cells

Back 119

OHC's are:
-active
-vulnerable
-mainly efferent
-biomechanical effectors

IHCs are:
-passive
-less vulnerable
-mainly afferent
-passive detectors

Front 120

Cochlear Amplifier Function

Back 120

-talking about the OHCs for sounds up to 40-60 dB SPL

-soft up to moderate, the hair cells dance, but the hair cells quit dancing when the sounds get louder to avoid overstimulation

efferent fibers - provide feedback to stop dancing because sound is too loud

Front 121

Cochlear potentials

Back 121

1. Resting Potential

Front 122

How hot is the EAM?

Back 122

98.6 degrees

Front 123

What way does the eardrum displace if the pressure in the middle ear is unbalanced?

Back 123

inward

Front 124

The cocleariform process is associated with what muscle?

Back 124

Tensor Tympani

Front 125

Ligament bands from the notch of Rivinus to malleus that hold ossicle bones to ear drum

Back 125

anterior and posterior malleolar folds

Front 126

Groove in bony wall of the EAM that holds the tympanic membrane

Back 126

Tympanic Sulcus

Front 127

Muscle that opens the Eustachian tube

Back 127

Tensor Veli Palatini

Front 128

Bony prominence that the stapedius comes out of

Back 128

pyramidal eminence

Front 129

Does the tympanic membrane move simply back and forth?

Back 129

No. It's a complex vibrator

Front 130

You can see the manubrium through the TM. this is called...

Back 130

Malleolar Stria

Front 131

The Eustachian tube connects the ___ wall of the middle ear with the ____?

Back 131

front/anterior
nasopharynx

Front 132

This ligament holds the malleus from the base of the neck in the middle ear cavity

Back 132

Anterior Process

Front 133

The 7th Cranial Nerve is also called...what part of the tongue does it innervate?

Back 133

Chorda Tympani
anterior 2/3 of tongue

Front 134

What is the Superior Boundary of the middle ear?

Back 134

Tegmental

Front 135

What is the inferior boundary of the middle ear?

Back 135

Jugular