Anatomy & Physiology of the Ear and Physiology and Clinical Aspects of Hearing & Balance

Question 1

What is the anatomy of the external ear?

Answer 1

Auricle:

• Large outside rim is called helix
• Tragus is the flap sitting just above the EAM
• Muscles of the auricle are innervated by the facial nerve

External Auditory Meatus:

• Tympanic Membrane

Question 2

What is the epithelial lining of the external and middle ear?

Answer 2

External ear - Stratified keratinized epithelium

Middle ear - Ciliated columnar epithelium with goblet cells

Question 3

What is the structure of the TM?

Answer 3

• Handle of Malleus
• Cone of light
• Umbo
• Incus

Question 4

What are the 2 areas of the middle ear?

Answer 4

• Epitympanic recess
• Tympanic cavity

Question 5

How does the middle ear communicate with other areas of the head & neck?

Answer 5

• Communicates with mastoid area posteriorly
• Communicates with nasopharynx anteriorly via the pharyngotympanic tube

Question 6

What is the function of the middle ear?

Answer 6

• Its basic function is to transmit the vibrations from the TM across the middle ear cavity to the inner ear

Question 7

What are the ossicles of the middle ear?

Answer 7

• Malleus (attached to TM at one end, Incus at the other via a synovial joint)
• Incus (connected to malleus and stapes by synovial joints)
• Stapes (connected to oval window of the inner ear)

Question 8

What is the importance of the Eustachian tube in middle ear function?

Answer 8

Equalizes pressure on both sides of the TM

Question 9

What muscles are associated with the middle ear ossicle?

Answer 9

1) Tensory tympani - Tenses the TM in order to stop any damage caused by loud nosies
2) Stapedius - Pulls the stapes bone in order to prevent over vibration caused by loud noises

Question 10

Where does the pharyngotympanic tube open within the pharynx?

Answer 10

Posterior to the Inferior meatus

Question 11

What is the innervation of the middle ear?

Answer 11

Tympanic nerve - branch of Glossopharyngeal nerve

Question 12

In which bone is the inner ear located?

Answer 12

Petrous part of Temporal bone

Question 13

What makes up the bony labyrinth of the inner ear?

Answer 13

• Vestibule
• 3 semicircular canals
• Cochlea

Question 14

What fills the structures of the bony labyrinth?

Answer 14

Perilymph

Question 15

What structures make up the membranous labyrinth?

Answer 15

Semi-circular ducts

Cochlear duct (organ of hearing and contains scala tympani and scala vestibule)

Utrile & Saccule - filled with endolymph

Question 16

What types of movement do the utricle, saccule and semicricular canals detect?

Answer 16

Semicircular canals - Head rotation

Saccule - Vertical movement

Utricle - Horizontal movement

Question 17

How is sound transmitted from middle ear onto the inner ear and then from vestibulocochlear nerve onto the brain?

Answer 17

1) Vibrations in the middle ear travel to the stapes bone
2) Foot of the stapes bone vibrates on the oval window
3) Vibrations on oval window create a pressure wave that travels through the fluid in cochlea.
4) This pressure wave is detected by hairs in the organ of corti
5) Signals from these hairs are transmitted to the brainstem (junction fo pons & medulla) by cranial nerve VIII.

Question 18

What are the principles of pure tone audiometry and tympanometry?

Answer 18

Pure Tone Audiometry - Air conduction hearing test to determine the faintest tones a person can hear

Tympanometry - A test which pushes air pressure into the ear canal to measure the mobility of the eardrum