Anatomy of the Ear

Question 1

External ear: where is it? function?

Answer 1

from the pinna to the ear drum (tympanic membrane)

receives sound waves

Question 2

What parts make up the middle ear and what is its function?

Answer 2

ear drum + chamber including eustachian tube (ossicular chain, oval window, round window, facial nerve, mastoid air cells)

Transmits sound waves from air to bone
Amplifies bone to bone
Transmits sound to inner ear

Question 3

What makes up the inner ear and what is its function?

Answer 3

Made up of the semi-circular canal and cochlea

sound waves converted to nerve impulses
Transmitted to CNS via acoustic nerve CN VIII
Vestibular organs - contributes to sense of balance and spatial orientation

Question 4

What is the Pinna lined with?

Answer 4

stratified keratinised epithelium - normal skin

This overlies the framework of elastic cartilage

Question 5

Where does the cartilage in the ear get its blood supply from?

Answer 5

Overlying dense connective tissue/perichondrium

Question 6

Describe the external ear canal

Answer 6

made up of 2 parts:-
- lateral 1/3 is made of skin and cartilage
In this part, the skin contains modified sweat glands that produce a protective wax layer (ceruminous and sebaceous glands). Also has thick hairs on outside

• medial 2/3 is made of skin and bone
  There are no hairs or cilia here and no wax is produced

Question 7

How does the skin grow in the ear

Answer 7

from the umbo of the tympanic membrane outwards and it then sheds in the lateral 1/3 of the canal - this is trapped in the wax and cleared by conveyor belt system

Question 8

What is otitis media?

Answer 8

inflammation of the external ear

It can be bacterial (pseudomonas or staph aureus) or fungal.

Question 9

Treatment for otitis media: what is important to remember when treating bacterial otitis media

Answer 9

pseudomonas need specific antibiotic treatment e.g ciprofloxacin
some medication that would work for staph aureus has no effect on pseudomonas bacteria

Question 10

Describe what you would see through an otoscope of a right ear drum?

Answer 10

Handle of malleus is slightly anterior along with the cone of light and the temperomandibular joint

The cone of light may not be present in otitis media remember

Question 11

Describe the structure of the tympanic membrane

Answer 11

Has 3 layers
outer layer is continuous with the skin of the external ear
Middle is a fibrous layer
Cuboidal epithelium

1cm diaemter
1/10th mm thick

Question 12

what is the function of the ossicles?

Answer 12

3 bones that play a very important role in sound conduction (more so than tympanic membrane).

Conduct sound waves from the TM to the inner ear via the oval window

Question 13

what are the names of the ossicles (3)

Answer 13

Malleus (hammer)
Incus (anvil)
Stapes (stirrup)

Question 14

What role does the external ear play in hearing?

Answer 14

TRANSDUCES THE VIBRATION INTO NERVOUS IMPULSES

Directs sound into the canal 
TM vibrates 
Ossicular chain vibrates 
Transmitted to oval window of cochlea 
Detected by hair cells in organ of corti
converted into nerve impulses and then transmitted to the brainstem

Question 15

which cranial nerve transmits nerve impulses to the brain stem

Answer 15

CN VIII

Question 16

what connects the middle ear to the nasopharynx?

Answer 16

the eustachian tube

Question 17

functions of the eustachian tube?

Answer 17

pressure equalisation
mucus drainage

it doesn’t always work well

Question 18

What is acute otitis media

Answer 18

Infection of the lining of the middle ear
- can be bacterial or viral
often caused by respiratory infections that spread via the eustachian tube

You get a red TM and pus in middle ear

Pain can improve if the TM perforates but if not it builds up and can spill over into the mastoid air sacs and cause mastoiditis - this requires a procedure to remove the pus

Question 19

What is otitis media with Effusion

Answer 19

This can occur when the eustachian tube is not opening so there is a negative pressure in the ear - fluid is drawn in which limits the mobility of the ossicular chain - this causes hearing loss

occurs easily in children - narrow E tube

Question 20

What can be put in place if an ear hasn’t gone back to normal after 3 months of OM with effusion?

Answer 20

grommets - do the same job as eustachian tube would (presssure etc) - they should fall out over time

Question 21

What is a cholesteatoma?

Answer 21

benign condition - abnormal skin growth

Negative pressure in the ear sucks in the TM which creates a retraction pocket where skin grows into

keritinase - eats into inner ear or into middle cranial fossa - slowly destroys structures

can be congenital

Question 22

What are the 6 segments of the facial nerve (CN VII)

Answer 22

Intracranial
Meatal segment 
Labyrinthine segment
Tympanic segment 
Mastoid segment
Extratemporal segment

Question 23

Where does the facial nerve start

Answer 23

at the cerebellopontine angle

Question 24

What does the facial nerve innervate

Answer 24

Gives motor supply to the muscles of facial expression
- stapedius, posterior belly of digastric and stylohyoid

Special sensory - taste - to the anterior 2/3 of the tongue

also gives parasympathetic innervation to the submandibular, sublingual and lacrimal glands

Question 25

What are the 5 branches of the facial nerve

Answer 25

Temporal
Zygomatic
Buccal
Marginal mandibular 
Stylohyoid

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Question 26

How can you tell if it patient has upper motor neurone facial palsy?

Answer 26

the forehead is unaffected - innervation from contralateral side

Question 27

What is the cochlear?

Answer 27

sense organ that translates sound into nerve impulses to be sent to the brain. Has 3 compartments.
Organ of corti sits in one of these.

It is a bony and membranous labyrinth. It contains fluid called perilymph and endolymph

Question 28

Which cranial nerve is involved in the transmission of nerve impulses from the cochlea to the brain?

Answer 28

vestibulocochlear nerve (CN VIII)

Question 29

What are the most common head and neck cancers?

Answer 29

Pharyngeal
Laryngeal
Nasopharyngeal

Question 30

What innervates the middle ear

Answer 30

Glossopharyngeal nerve (CN IX)

Question 31

What innervates the posterior part external ear

Answer 31

auricular branch of vagus nerve (CN X)

Question 32

What innervates the anterior part of external ear

Answer 32

Facial nerve

Question 33

What innervates the Pinna?

Answer 33

Mandibular branch of the trigeminal nerve (CN V3)