Chapter 9. Functional Anatomy of the Ear

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Functional Anatomy of the Ear

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The ear is our link to the world of sound, including speech and music.
Photo: © Blend Images / Alamy.

What Is the Functional Anatomy of the Ear?

The ear is conventionally divided into three parts—the outer ear, middle ear, and inner ear. The outer ear consists of the pinna, the auditory canal, and the tympanic membrane. The pinna gathers sound waves from the environment, and the auditory canal funnels the sound waves onto the tympanic membrane, which vibrates in response. Those vibrations are transmitted into the middle ear, a tiny air-filled chamber containing the ossicles—three small bones called the malleus, the incus, and the stapes. The air pressure on the outer side of the tympanic membrane must be approximately equal to the air pressure on the inner side. This is accomplished via the Eustachian tube, which connects the middle ear to the top part of the throat.

The ossicles transmit sound energy from the tympanic membrane to the inner ear, which contains the cochlea and the semicircular canals (involved in the sense of balance and acceleration, not audition). The malleus is connected to the tympanic membrane, so when the tympanic membrane vibrates, the malleus pushes on the incus, which in turn displaces the stapes, which then pushes in on the oval window, a membrane-covered opening at the base of the cochlea. This creates vibrations within the cochlea, and neurons in the cochlea transduce the vibrations into neural signals that are sent to the brain via the auditory nerve.

The cochlea is a snail-shaped compartment partitioned along its length into three fluid-filled chambers—the vestibular canal, the cochlear duct, and the tympanic canal. Reissner's membrane separates the vestibular canal from the cochlear duct, and the basilar membrane separates the cochlear duct from the tympanic canal. Within the cochlear duct, resting on the basilar membrane, is the structure responsible for auditory transduction, the organ of Corti.

The organ of Corti contains two sets of neurons—inner hair cells and outer hair cells—and the tectorial membrane, which lies above the hair cells. Each hair cell has stereocilia protruding from the top. Open spaces within the organ of Corti are filled with endolymph, the fluid inside the cochlear duct. The stereocilia atop the hair cells are bent back and forth as a result of the movements of the basilar and tectorial membranes, and this bending of the stereocilia causes the hair cells to produce neural signals that are conveyed to the brain. Inner hair cells are connected to Type I auditory nerve fibers; outer hair cells are connected to Type II auditory nerve fibers.





9.2 Explain - dnd

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Drag and drop each label into the correct box on this illustration of the ear.

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Inner ear
Stapes
Ossicles
Cochlea
Middle ear
Semicircular canals
Malleus
Outer ear
Tympanic membrane
Auditory canal
Eustachian tube
Auditory nerve
Incus
Pinna

9.3 Explain - dnd

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Drag and drop each label into the box with the correct definition of these parts of the ear.

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Structures involved in the sense а balance and acceleration, not audition
A coiled, tapered tube partitioned into three chambers
A thin, elastic diaphragm at the inner end of the auditory canal
One of thе ossicles; transmits vibrations from the eardrum to the incus
A tiny air-filled chamber that contains the ossicles
Three small bones in the middle ear
The outermost part of the ear
Funnels sound waves onto the tympanic membrane
One of the ossicles; transmits vibrations from the malleus to the stapes
Connects the middle ear and the top part of the throat
The parts of the ear that can be seen from outside the body
One of thе ossicles; transmits vibrations from the incus to the cochlea
Contains the cochlea and the semicircular canals
Carries neural signals from the ear to the brain
Inner ear
Stapes
Ossicles
Cochlea
Middle ear
Semicircular canals
Malleus
Outer ear
Tympanic membrane
Auditory canal
Eustachian tube
Auditory nerve
Incus
Pinna

9.4 Explain - dnd

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Drag and drop each label into the correct box on these views of the cochlea.

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Cochlea
Cross Section of Cochlea
Tympanic canal
Organ of Corti
Vestibular canal
Basilar membrane
Oval window
Reissner's membrane
Cochlear duct
Round window
Auditory nerve

9.5 Explain - dnd

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Drag and drop each label into the box with the correct definition of these parts of the cochlea.

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Cochlea
Cross Section of Cochlea
One of three chambers in the cochlea; separated from the cochlear duct by the basilar membrane
One of three chambers of the cochlea; separated from the cochlear duct by Reissner's membrane
One of three chambers in the cochlea; contains the organ of Corti
Separates the vestibular canal from the cochlear duct
Consists of inner hair cells, outer hair cells, and the tectorial membrane
Carries neural signals from the hair cells in the organ of Corti to the brain
A membrane-covered opening at the base of the tympanic canal
Membrane supporting the organ of Corti
A membrane-covered opening at the base of the vestibular canal
Oval window
Round window
Auditory nerve
Vestibular canal
Reissner's membrane
Cochlear duct
Organ of Corti
Basilar membrane
Tympanic canal

9.6 Explain - dnd

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Drag and drop each label into the correct box on this illustration of the organ of Corti.

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Tectorial membrane
Endolymph
Type I auditory nerve fiber
Basilar membrane
Outer hair cell
Type II auditory nerve fiber
Stereocilia
Inner hair cell

9.7 Explain

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What Is the Functional Anatomy of the Ear?

The ear is conventionally divided into three parts—the outer ear, middle ear, and inner ear. The outer ear consists of the pinna, the auditory canal, and the tympanic membrane. The pinna gathers sound waves from the environment, and the auditory canal funnels the sound waves onto the tympanic membrane, which vibrates in response. Those vibrations are transmitted into the middle ear, a tiny air-filled chamber containing the ossicles—three small bones called the malleus, the incus, and the stapes. The air pressure on the outer side of the tympanic membrane must be approximately equal to the air pressure on the inner side. This is accomplished via the Eustachian tube, which connects the middle ear to the top part of the throat.

The ossicles transmit sound energy from the tympanic membrane to the inner ear, which contains the cochlea and the semicircular canals (involved in the sense of balance and acceleration, not audition). The malleus is connected to the tympanic membrane, so when the tympanic membrane vibrates, the malleus pushes on the incus, which in turn displaces the stapes, which then pushes in on the oval window, a membrane-covered opening at the base of the cochlea. This creates vibrations within the cochlea, and neurons in the cochlea transduce the vibrations into neural signals that are sent to the brain via the auditory nerve.

The cochlea is a snail-shaped compartment partitioned along its length into three fluid-filled chambers—the vestibular canal, the cochlear duct, and the tympanic canal. Reissner's membrane separates the vestibular canal from the cochlear duct, and the basilar membrane separates the cochlear duct from the tympanic canal. Within the cochlear duct, resting on the basilar membrane, is the structure responsible for auditory transduction, the organ of Corti.

The organ of Corti contains two sets of neurons—inner hair cells and outer hair cells—and the tectorial membrane, which lies above the hair cells. Each hair cell has stereocilia protruding from the top. Open spaces within the organ of Corti are filled with endolymph, the fluid inside the cochlear duct. The stereocilia atop the hair cells are bent back and forth as a result of the movements of the basilar and tectorial membranes, and this bending of the stereocilia causes the hair cells to produce neural signals that are conveyed to the brain. Inner hair cells are connected to Type I auditory nerve fibers; outer hair cells are connected to Type II auditory nerve fibers.

9.8 Test - dnd

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wfN2f02Mdl0Zhut2ksq2+3CebDOb62p9pU4mHbICu/I=
Slide 8/Test Yourself 1 Matching Activity

The ear transduces sound waves into neural signals. Drag the labels into the empty boxes to show the order of events in this process. Then click SUBMIT.

Sound waves
Neural signals
Sound waves enter the ear
Neurals signals are sent to the brain

Stereocilia on hair cells bend

Tympanic membrane vibrates

Hair cells produce neural signals

Ossicles vibrate

Basilar membrane is displaced

Waves travel in cochlear fluid

9.9 Test - single choice

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Rky+uyOUdifqhAALa92IEfLct+uT+wjLX2QlmQJAHsGS1XtES+G9qsGwVftP9al7eLkiLz0DMZoN+fBAWL3x9/nfn+mZFS5gikrI2XNgRRR/KMxumtD/awtk+jRyfikUHa4VtSrUoW36l1Fc2x3841DWjyy8sh+FPYdAdMRup86wmBg6aTAHjPdoO9QMfD0+gcI29MtnbNIn+oeuWharZACe2q28P5L/YhAl9OE9zlnilWp6T1T+WT0UQCM/Rom44TwwqYojLp3cJeEU9di6H9gioiYfyNsQG0DbXojy3CrmlpLrYM0t49XyTbadwQhixR23W6+HzGRFvQJS4N0gbyu846bBzbGI/Bb2/fmQ3abMgm3zmWGCipPqijAo9eg80rLIgqA2/yUbYlUlqr96sMyhvyAymPHGYCU22CPy+8KlUJ0BkKRfhay/89D/9vCC91GGHQ==
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9.10 Test - single choice

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