9) Anatomy of the Ear

Question 1

What are the general functions of the ear?

Answer 1

Hearing and balance

Question 2

What are the three parts of the ear?

Answer 2

External, middle and inner

Question 3

What are some general symptoms that point towards the diagnosis of ear disease?

Answer 3

Otalgia (pain)
Discharge 
Hearing loss
Tinnitus
Vertigo

Question 4

In which bone is the ear found?

Answer 4

Petrous part of temporal bone

Question 5

What is the function of the external ear?

Answer 5

Collects, transmits and focuses sound waves onto tympanic membrane

Question 6

What does the external ear consist of?

Answer 6

Pinna, external auditory meatus and lateral surface of tympanic membrane

Question 7

Describe the structures forming the pinna:

Answer 7

Outer rim: helix
Inner fold: antihelix
Inferior: lobule
Entrance to EAM: tragus, concha and antitragus

Question 8

What is a pinna haematoma?

Answer 8

Blood collects between cartilage and perichondrium causing loss of blood supply to cartilage and pressure necrosis of tissue

Question 9

What can cause a pinna haematoma?

Answer 9

Blunt injury to pinna

Question 10

What is the treatment for a pinna haematoma?

Answer 10

Drainage and re-apposition of layers

Question 11

What can occur if the external ear is repeatedly damaged?

Answer 11

Fibrosis and asymmetrical cartilage development = cauliflower ear

Question 12

Describe the external acoustic meatus:

Answer 12

2.5cm long skin lined canal in a sigmoid shape (pull ear up and back when examining)
Cartilaginous laterally and bony medially

Question 13

Where are hairs and wax found in the ear and what are their functions?

Answer 13

On cartilaginous portion

Prevent objects entering deeper canal and aids desquamation and skin migration out of canal

Question 14

What is otitis externa?

Answer 14

Inflammation of external ear (swimmer’s ear)

Question 15

Describe the tympanic membrane:

Answer 15

Fibrous CT structure that is pearly and translucent

Question 16

What features can be seen on the tympanic membrane when examining the ear?

Answer 16

Outline of malleus stretching down in the middle
Attic
Pars tensa
Cone of light (points right in right ear)

Question 17

How can the tympanic membrane be damaged?

Answer 17

Perforation due to infection, pressure or trauma

Question 18

What is otitis media and how does it look on examination?

Answer 18

Acute middle ear infection

Red, bulging, featureless ear drum

Question 19

What does the middle ear consist of?

Answer 19

Ossicles: malleus, incus and stapes

Tympanic cavity and epitympanic cavity (high)

Question 20

What is the function of the ossicles?

Answer 20

Amplify vibration from tympanic membrane to cochlea via oval window

Question 21

How are the middle ear and nasopharynx connected?

Why?

Answer 21

Eustachian tube - allows equilibration of pressure within middle ear cavity with atmosphere

Question 22

What is otitis media with effusion?

Answer 22

Build up of fluid and negative pressure in middle ear as Eustachian tube is closed, so cells in middle ear absorb air

Question 23

How does otitis media with effusion affect the ear, and hence how does it commonly present?

Answer 23

Decreases mobility of tympanic membrane and ossicles

Effects hearing and performance in school

Question 24

What is the treatment for glue ear?

Answer 24

Spontaneous resolution or grommets - plastic ventilation tube through tympanic membrane

Question 25

What are some complications of otitis media?

Answer 25

Tympanic membrane perforation Facial nerve involvement Mastoiditis or intracranial infections

Question 26

What structures run close to the ear?

Answer 26

ICA, sigmoid sinus, mastoid cells, CN VII (chorda tympani) and VIII

Question 27

What is mastoiditis?

Answer 27

Infection that spread to air cells of mastoid process

Question 28

What is cholesteatoma?

Answer 28

Negative pressure draws ear drum inwards and leads to small pocket where skin cells collect and grow. Can erode structures

Question 29

What causes cholesteatoma?

Answer 29

Chronic/recurring ear infections | Blockage of Eustachian tube

Question 30

What does the inner ear consist of?

Answer 30

Cochlea, semicircular canals and vestibule (utricle and saccule)

Question 31

Describe the features of the cochlea:

Answer 31

Bony and membranous labyrinth (cochlear duct) | Round and oval window

Question 32

Describe how we hear:

Answer 32

Vibration of ossicles sets up vibrations in cochlear fluid (endolymph) -> sensed by nerve cells in cochlear duct (spiral organ of Corti) -> movement of these receptors trigger AP in CN VIII -> brain

Question 33

Describe how the vestibular apparatus is involved in balance:

Answer 33

Fluid filled series of channels and sacs that respond to position rotation and maintain balance

Question 34

What is conductive hearing loss?

Answer 34

From cochlea outwards, problem conducting sound

Question 35

What is sensorineural hearing loss?

Answer 35

Problem with CN VIII or in cochlea

Question 36

What is vertigo?

Answer 36

Dizziness with spinning sensation

Question 37

What is Meniere's disease?

Answer 37

Attacks of vertigo, hearing loss and tinnitus

Question 38

What is Benign Paroxysmal Positional Vertigo?

Answer 38

Attacks of vertigo when move head in certain direction

Question 39

What is Ramsay-Hunt Syndrome and how does it present?

Answer 39

Shingles in CN VII | Vesicles on pinna and facial nerve palsy

Question 40

Describe the results of Weber's and Rinne's test for conductive hearing loss:

Answer 40

Sound towards affected ear | Bone conduction greater than air conduction in affected ear

Question 41

Describe the results of Weber's and Rinne's test for sensorineural hearing loss:

Answer 41

Sound away from affected ear | Air conduction better than bone conduction but both bad

Question 42

What can cause hyperacusis?

Answer 42

Damage to nerve to stapedius (CN VII)