The Auditory System (Ch 9)

Question 1

Outer Ear is made of?

Answer 1

Pinna, External Auditory Meatus (EAM)

Question 2

Pinna is made of?

Answer 2

Flexible elastic cartilage, soft lobule

Question 3

Primary function of the Pinna?

Answer 3

Direct sound waves into the ear canal

Question 4

Secondary function of the Pinna

Answer 4

Assists with localization of sound (two pinnae) and protects entrance to ear canal

Question 5

External Auditory Meatus is made of?

Answer 5

Bone (medial) and cartilage (lateral)

Question 6

EAM is lined with?

Answer 6

A layer of epidermis and lateral portion contains glads that secrete cerumen and cilia

Question 7

Making function of the EAM?

Answer 7

Protects middle and inner ear. Lubricates ear and protect insects entering. Moves dust and small particles out of the ear.

Question 8

Describe the shape and appearance of the Tympanic Membrane (TM)

Answer 8

Thin, semi-transparent membrane separating outer and middle ear. Concave shape, with tip (umbo) facing middle ear.

Question 9

What does the TM do?

Answer 9

Vibrates when sound (acoustic pressure) waves hit it. Then converts pressure waves to mechanical vibration via connection with malleus.

Question 10

The middle ear is made up of what three things?

Answer 10

ossicles, eustachian tube, muscles

Question 11

What are the three ossicles in the middle ear?

Answer 11

Malleus, Incus, and Stapes

Question 12

What shape is the malleus, and what does it do?

Answer 12

Hammer, connected to the TM and when it vibrates the malleus vibrates as well, beginning the ossicular vibratory chain.

Question 13

Incus aka….?

Answer 13

The anvil! Connected to the malleus which sets incus into vibration.

Question 14

Where is the stapes located?

Answer 14

Also called the stirrup, head of stapes is connected to the incus and the footplate of the stapes covers the oval window.

Question 15

How long is the Eustachian tube?

Answer 15

approx. 35 mm

Question 16

What does the Eustachian tube connect?

Answer 16

The middle ear cavity to nasopharynx. The Pharyngeal end of tube is normally closed (opens for swallowing and yawning). Middle ear end of tube is normally open.

Question 17

What does the Eustachian tube do?

Answer 17

keeps middle air space ventalized (equalizes air pressure) and drained (clears mucus by draining into pharynx)

Question 18

Name the two middle ear muscles

Answer 18

Tensor Tympani and Stapedius muscle

Question 19

Describe the location and function of the Tensor Tympani.

Answer 19

Runs parallel to eustachian tube. Contracts to move malleus inward, tensing the TM and damping vibration in the ear ossicles, reducing the perceived amplitude of sound. It’s approx. 20 mm in length.

Question 20

Describe the function of the Stapedius muscle

Answer 20

contacts to pull stapes posteriorly and tense membrane in oval window. Approx. 1 mm in length.

Question 21

Define the stapedial reflex

Answer 21

Contracts strongly in response to intense sound (80 dB +), stiffening membrane and reducing amplitude of vibration. Less effective in noisy environments.

Question 22

What are the three parts of the Inner Ear?

Answer 22

Cochlea, vestibule, and semicircular canals

Question 23

Describe the cochlea.

Answer 23

Bony, spiral canal with 2 ¾ turns around boney core (modiolus). Inside membranous canal, called the cocker duct. The space between the bony canal and membranous canal is filled with fluid, called perilymph. The membranous canal is filled with fluid called endolymph.

Question 24

What is the base of the cochlea?

Answer 24

The basilar membrane (BM)

Question 25

What is the roof of the cochlear duct?

Answer 25

the vestibular

Question 26

What is the scala vestibuli

Answer 26

the space above the vestibular

Question 27

What is the space below the Basilar membrane?

Answer 27

scala tympani

Question 28

Where is the organ of corti?

Answer 28

sitting on basilar membrane (lined with inner and outer hair cells)

Question 29

Describe the Basilar Membrane

Answer 29

Width increases from base (.04 mm) to apex (.36mm) (opposite to width changes of bony cochlea). Stiffness increases from base to apex (100x more stiff). BM is more responsive to high frequencies at base and lower frequencies at apex.

Question 30

Describe the Vestibule

Answer 30

Central portion of the inner ear. Located behind the cochlea and in front of the semicircular canals. It is 5 mm in length. AKA the “Entrance hall”

Question 31

Describe the semicircular canals

Answer 31

Three canals/rings which house the sense organs for movement of the body in space.

Question 32

Name the three semicircular canals

Answer 32

horizontal/lateral, Anterior/superior, posterior

Question 33

What does the Horizontal canal do?

Answer 33

Detects rotation of the head around transverse body plane (e.g. when you turn your head to the left and right hand sides before crossing a road). Shortest canal (12-15 mm).

Question 34

What does the Anterior Canal do?

Answer 34

Detects rotation of the head around coronal body plane (e.g. when you move your head to touch your shoulders or when doing a cartwheel). It is 15-20 mm, vertical in direction.

Question 35

What does the Posterior Canal do?

Answer 35

Detects the rotation of the head around sagittal body plane (e.g. when nodding your head). It is 18-22 mm, vertical in direction.

Question 36

List four common hearing disorders of the middle ear.

Answer 36

Eustachian tube dysfunction, tympanic membrane perforation, otitis media, external otitis media (aka swimmers ear)

Question 37

Otitis Media

Answer 37

Most common cause of conducive hearing loss (25-30 dB). Most common in young children but can occur at any age. Seen in nearly 70% of children under age two.

Question 38

Other disorders associated with conductive hearing loss.

Answer 38

Wax impaction in the ear canal, atresia/microtia, otosclerosis and ossicular fusion, ossicular chain discontinuity, cholesteatoma, genetic or syndromic conditions

Question 39

What is Atresia?

Answer 39

no opening to canal

Question 40

What is Microtia?

Answer 40

malformed pinna (often has atresia in addition to microtia.

Question 41

Issues associated with Atresia/Microtia

Answer 41

Trencher collins, hemifactial microsomia, goldenhar, crouzon’s, pfeiffer, apert, nager/miller, klippel-feil, branchio-oto-renal, Pierre Robin, CHARGE

Question 42

What does BAHA stand for?

Answer 42

Bone Anchored Hearing Aid, it vibrates the mastoid bone, which bypasses the outer ear and goes straight to the inner ear.