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Figure 17-21 The Anatomy of the Ear

External Ear

Elastic cartilages

Auricle

External acousticmeatus

Tympanicmembrane

Tympaniccavity

Middle Ear

Auditory ossicles

Ovalwindow

Semicircular canals

Petrous part oftemporal bone

Facial nerve (N VII)

Cochlea

Vestibulocochlearnerve (N VIII)

Bony labyrinthof internal ear

Auditory tube

Tonasopharynx

VestibuleRoundwindow

Internal Ear

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Figure 17-22a The Middle Ear.

Temporal bone(petrous part)

Stabilizingligaments

Branch of facialnerve VII (cut)

Externalacoustic meatus

Malleus Incus Stapes

Auditory Ossicles

Muscles ofthe Middle Ear

Oval window

Tensor tympanimuscle

Stapedius muscle

Round window

Auditory tube

Tympanic cavity(middle ear)

Tympanic membrane

The structures of the middle eara

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Figure 17-22b The Middle Ear

Tendon of tensortympani muscleMalleus

Malleus attached totympanic membrane

Incus

Base of stapesat oval window

Stapes

Stapedius muscle

Inner surface oftympanic membrane

The tympanic membrane and auditory ossiclesp. 592

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© 2015 Pearson Education, Inc.

Figure 17-24a The Semicircular Ducts

Semicircular ductsAnterior

LateralPosterior

Ampulla

Utricle

Saccule Maculae

Vestibular branch (N VIII)

Cochlea

Endolymphatic sac

Endolymphatic duct

An anterior view of the right semicircular ducts, the utricle, and the saccule, showing the locations of sensory receptors

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Figure 17-25ab The Saccule and Utricle.

Endolymphatic sac

Endolymphatic duct

Utricle

Saccule

The location ofthe maculae

a

Otoliths

Gelatinous layerforming otolithic

membrane

Hair cells

Nerve fibers

The structure of an individual maculab

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Figure 17-25c The Saccule and Utricle

Head in normal, upright position

Gravity

GravityHead tilted posteriorly

Receptoroutput

increases

Otolithmoves

“downhill,”distorting haircell processes

A diagrammatic view of macular function when the head is held horizontally and then tilted back 2

1 p. 596

© 2015 Pearson Education, Inc.

Figure 17-24a The Semicircular Ducts.

a

Semicircular ducts

Anterior

Posterior

Lateral

Ampulla

Utricle

Vestibular branch (N VIII)

Cochlea

Endolymphatic sac

Endolymphatic duct

Maculae

Saccule

An anterior view of the rightsemicircular ducts, the utricle,and the saccule, showing thelocations of sensory receptors.

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Figure 17-24b The Semicircular Ducts

Cupula

A cross section through theampulla of a semicircular duct

Crista

Supporting cells

Sensory nerve

Ampullafilled with

endolymph

Hair cells

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Figure 17-24c The Semicircular Ducts

Endolymph movement along the lengthof the duct moves the cupula andstimulates the hair cells.

At rest

Direction ofduct rotation

Direction of relativeendolymph movement

Semicircular duct

Direction ofduct rotation

Ampulla

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Figure 17-24d The Semicircular Ducts

StereociliaKinocilium

Hair cell

Sensorynerve endingSupportingcell

A representative hair cell (receptor) from thevestibular complex. Bending the sterocilia towardthe kinocilium depolarizes the cell and stimulatesthe sensory neuron. Displacement in the opposite direction inhibits the sensory neuron.

Displacement inthis directioninhibits hair cell

Displacement inthis direction

stimulates hair cell

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Figure 17-26 Pathways for Equilibrium Sensations.

Semicircularcanals

Vestibularganglion

Vestibularbranch

Vestibule

N VI

N IV

N III

Red nucleus

Vestibularnucleus

N XI

To cerebellum

Vestibulospinaltracts

To superior colliculus andrelay to cerebral cortex

Cochlearbranch

Vestibulocochlearnerve (VIII)

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Figure 17-27a The Cochlea.

Scala vestibuli

Cochlear duct

Scala tympani

Cochlearbranch

Vestibularbranch

Vestibulocochlearnerve (VIII)

Round window

Stapes atoval window

From oval windowto tip of spiral

From tip of spiralto round window

KEY

Semicircularcanals

The structure of the cochleaa

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Figure 17-27b The Cochlea

Vestibularmembrane

Tectorialmembrane

Basilarmembrane

From ovalwindow

To roundwindow

Temporal bone(petrous part)

Scala vestibuli(contains perilymph)

Cochlear duct(contains endolymph)

Spiral organ

Spiral ganglion

Scala tympani(contains perilymph)

Cochlear nerve

Vestibulocochlear nerve (N VIII)

Diagrammatic and sectional views of the cochlear spiral p. 598

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Figure 17-28a The Spiral Organ.

Bony cochlear wall

Scala vestibuli

Vestibular membrane

Cochlear duct

Tectorial membrane

Basilar membrane

Scala tympani

Spiral organ

Spiralganglion

Cochlear branchof N VIII

A three-dimensional section of thecochlea, showing the compartments,tectorial membrane, and spiral organ

a

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Figure 17-28b The Spiral Organ

Tectorial membrane

Outerhair cell

Basilar membrane Inner hair cell Nerve fibers

Diagrammatic and sectional views of the receptor hair cell complex of the spiral organ

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Figure 17-28b The Spiral Organ

Diagrammatic and sectional views of the receptor hair cell complex of the spiral organ

Spiral organ

Cochlear duct (scala media)

Basilarmembrane

Hair cellsof spiral

organ

Spiral ganglioncells of

cochlear nerveLM 125

Vestibular membrane

Tectorial membrane

Scala tympani

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Figure 17-31a Frequency Discrimination

Stapesat oval

window

Roundwindow

16,000 Hz

Basilar membrane

Cochlea6000 Hz 1000 Hz

The flexibility of the basilar membrane varies along its length, so pressurewaves of different frequencies affect different parts of the membrane.

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Figure 17-31b Frequency Discrimination

Stapesmovesinward

Roundwindowpushed

outward

Basilar membrane distortstoward round window

The effects of a vibration of the stapes at a frequency of 6000 Hz. Whenthe stapes moves inward, as shown here, the basilar membrane distortstoward the round window, which bulges into the middle-ear cavity.

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Figure 17-31c Frequency Discrimination

Stapesmoves

outwardRound

windowpulled

inward

Basilar membrane distortstoward oval window

When the stapes moves outward, as shown here, the basilarmembrane rebounds and distorts toward the oval window.

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Figure 17-30 Sound and Hearing

Externalacousticmeatus

Malleus Incus

Movementof sound

waves

Tympanicmembrane

Roundwindow

Stapes Oval window

Sound wavesarrive attympanicmembrane.

Movement ofthe tympanicmembrane causesdisplacementof the auditoryossicles.

Movement ofthe stapes atthe oval windowestablishespressurewaves in theperilymphof the scalavestibuli.

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Figure 17-30 Sound and Hearing (Part 2 of 2).

5

4

6

4 5 6

Cochlear branchof cranial nerve VIII

Scala vestibuli(contains perilymph)

Vestibular membrane

Cochlear duct(contains endolymph)

Basilar membrane

Scala tympani(contains perilymph)

The pressurewaves distortthe basilarmembrane ontheir way to theround windowof the scalatympani.

Vibration ofthe basilarmembranecauses hair cellsto vibrate againstthe tectorialmembrane.

Information aboutthe region andthe intensity ofstimulation isrelayed to the CNSover the cochlearbranch of cranialnerve VIII.htt

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http://scienceblogs.com/retrospectacle/2006/06/a_17khz_pain_in_the_ear.php

© 2015 Pearson Education, Inc.

Figure 17-32 Pathways for Auditory Sensations

Stimulation of hair cells ata specific location alongthe basilar membraneactivates sensory neurons.

Cochlea

Low-frequencysounds

High-frequencysounds

Vestibularbranch

KEY

Sensory neurons carry thesound information in thecochlear branch of thevestibulocochlear nerve (VIII)to the cochlear nucleus onthat side.

Primary pathwaySecondary pathway

Motor output

Vestibulocochlearnerve (VIII) p. 603

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Figure 17-32 Pathways for Auditory Sensations

KEYPrimary pathwaySecondary pathwayMotor output

Motor outputto spinal cordthrough the

tectospinal tracts

To reticular formation and motor nuclei of cranial nerves

Information ascends from each cochlearnucleus to the inferior colliculi of the midbrain.

The inferior colliculi direct a variety ofunconscious motor responses to sounds.

Ascending acousticinformation goes to themedial geniculate nucleus.

Low-frequencysounds

High-frequency

soundsThalamus

Projection fibers thendeliver the information tospecific locations withinthe auditory cortex of thetemporal lobe.

Tocerebellum

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Table 17-1 Intensity of Representative Sounds.

p. 600

http://www.healthtree.com/articles/auditory-system/hearing-testing-impairments/cochlear-implants/