1 Hearing anatomy and

Question 2

Which of the 3 parts of the ear is the location of most problems related to hearing loss?

Answer 2

The inner ear. Sensorineural is the most common type of hearing loss and it affects the inner ear.

Question 3

What are the three parts of the human ear?

Answer 3

The three parts of the human ear are the outer ear, middle ear, and inner ear.

Question 4

What psychological impacts are associated with untreated hearing loss?

Answer 4

Individuals with untreated hearing loss are more likely to report depression, anxiety, and paranoia and are less likely to participate in organized social activities compared to those who wear hearing aids.

Question 5

What is the motivation for studying Biomedical Acoustics?

Answer 5

360 million individuals suffer from hearing loss worldwide with 6-8% of the world population affected. 91% are adults and 9% are children. 11000 newborns suffer from hearing loss. 50% of individuals aged 65 and older suffer from significant hearing loss and up to 95% of those aged 80 and older suffer from significant hearing loss.

Question 6

What is the function of the outer ear?

Answer 6

The outer ear, also known as the external ear, consists of the pinna and the ear canal which transmit sound to the tympanic membrane (ear drum).

Question 7

What are the characteristics of the ear canal?

Answer 7

The ear canal is about 4 cm long in adults and consists of outer cartilage and an inner bony part. The cartilaginous portion has hairy skin containing sweat glands and oily sebaceous glands that produce ear wax, which is a protective barrier and disinfectant.

Question 8

What is the pinna’s structure and function?

Answer 8

The pinna collects sound and directs it into the ear canal. It is made of cartilage covered by skin and does not contribute to sound amplification.

It helps to localise sound

Question 9

Why is the ear canal bent?

Answer 9

To protect against foreign bodies. The start is cartilaginous but the deeper part is bony and does not have the ability to migrate wax and foreign bodies.

Question 10

What is cholesteatoma?

Answer 10

Cholesteatoma is an abnormal noncancerous skin growth in the ear that can destroy the delicate bones (ossicles) in the middle ear affecting hearing and balance. Treatment usually involves surgical removal.

Question 11

What is the structure and function of the tympanic membrane?

Answer 11

The tympanic membrane is a thin layer of skin on the outside and a thin membrane of respiratory epithelium on the inner surface with a stiffening fibrous middle layer called pars tensa. It is less than 1/10th of a millimeter thick.

Question 12

What is the middle ear?

Answer 12

The middle ear is an air-filled space that houses the malleus, incus, and stapes bones which conduct sound from the tympanic membrane to the inner ear.

Question 13

What does the footplate of the stapes cover?

Answer 13

The oval window (opening to the cochlea).

Question 14

What are the three bones of the middle ear?

Answer 14

The three bones of the middle ear are the malleus, incus, and stapes.

Question 15

Which 2 sensory organs does the inner ear contain?

Answer 15

The inner ear contains the cochlea (hearing) and the vestibular system (balance).

Question 16

What is the cochlea?

Answer 16

The cochlea is the inner ear organ shaped like a snail shell (2.5 turns) that houses the organ of hearing (organ of Corti) and is involved in sound perception.

Question 17

What is the Eustachian tube and its function?

Answer 17

The Eustachian tube links the nose to the middle ear helping to equalize air pressure in the middle ear and the nose.

In adults it is approximately 35mm long and 3mm in diameter

Question 18

What role do hair cells play in hearing?

Answer 18

Hair cells transduce vibrations into nervous impulses with inner hair cells responsible for transmitting signals to the brain and outer hair cells acting as amplifiers.

Question 19

Where is the basilar membrane located?

Answer 19

The basilar membrane is located in the cochlea of the inner ear.

Question 20

How many hair cells and nerve fibers does the inner ear contain?

Answer 20

30000 hair cells and 19000 nerve fibers.

Question 21

What fluids fill the cochlea?

Answer 21

The cochlea contains two types of fluids: perilymph in the scala vestibuli and scala tympani and endolymph in the membranous labyrinth (scala media).

Question 22

What is the normal human (newborn) hearing range (Hz)?

Answer 22

16 Hz to 20000 Hz.

Most sensitive to 128 Hz to 4000 Hz (range of human voice).

Question 23

What is the relationship between sound frequency and cochlear response?

Answer 23

High frequencies deflect the base of the cochlear duct while low frequencies deflect the apex. Different parts of the cochlear duct respond to different sound frequencies (because of Basilar membrane).

Question 24

How are hair cells arranged?

Answer 24

There are 4 rows of hair cells on top of the basilar membrane:
1 row of inner hair cells and 3 rows of outer hair cells. Inner hair cells have an abundant nerve supply (compared to outer cells).

Question 25

How do the different hair cells interact with the tectorial membrane?

Answer 25

Outer hair cells are firmly attached to the membrane. Inner hair cells are either free standing or loosely attached to the membrane.

Question 26

What happens to the middle ear during a flight?

Answer 26

When flying, the pressure in the middle ear and the outside environment may not match causing the Eustachian tube to become blocked. Swallowing or yawning can help equalize the pressure.

Question 27

What is sensorineural hearing loss?

Answer 27

Sensorineural hearing loss is the most common type of hearing loss that occurs due to damage to the inner ear’s sensory cells or the nerve pathways from the inner ear to the brain.

Can only be treated with technical devices and not with surgery or medication.

Question 28

What happens to hair cells when they are damaged?

Answer 28

Once hair cells are damaged there is no recovery. Hearing aids can be used to amplify sound if OHC are damaged. But if IHC are damaged cochlear implants may be needed to generate a direct electronic signal for hearing.

Question 29

What is the purpose of the inner hair cells?

Answer 29

They are responsible for the transduction of vibrations to a nerve impulse.

Question 30

What is the general mechanism of sound conduction in the ear?

Answer 30

Sound waves collected by the pinna travel through the ear canal vibrating the tympanic membrane. The auditory ossicles then vibrate and amplify the pressure with the stapes creating pressure waves in the cochlea.

Question 31

What are the characteristics of the audible range of human hearing?

Answer 31

The audible range is approximately 10 octaves from 16 Hz to 20000 Hz with the highest sensitivity around 128 Hz to 4000 Hz.

Question 32

What is the purpose of the outer hair cells?

Answer 32

They act as amplifiers. They change their length with muscle proteins.

Question 33

If the movement of the basilar membrane is slight, what do the outer hair cells do?

Answer 33

If the movement of the basilar membrane is slight, the outer hair cells amplify the sound.