The External and Middle Ear

Question 1

Innervation of the auricle?

Answer 1

Cutaneous innervation

-greater auricular, lesser occipital and branches of facial and vagus nerves

Question 2

Why can cleaning your ears sometimes cause you to cough?

Answer 2

Can stimulate the auricular branch of the vagus nerve

Vagus nerve is responsible for the cough reflex.

Question 3

Vasculature of the auricle?

Answer 3

Posterior auricular, superficial temporal, occipital arteries and veins

Question 4

What is the external acoustic meatus?

Answer 4

Sigmoid shaped tube extending from the deep part of the concha to the tympanic membrane

Question 5

What gives the external acoustic meatus structure?

Answer 5

Cartilage from the auricle

Bony support from the temporal bone

Question 6

Innervation of the external acoustic meatus?

Answer 6

Sensory innervation

-branches of the mandibular and vagus nerve

Question 7

Describe the direction that the external acoustic meatus travels

Answer 7

Initially superioanterior
Then superioposterior
Then inferioanterior

Question 8

What are the two layers of the tympanic membrane?

Answer 8

Skin on the outside
Mucous membrane on the inside
Core of connective tissue

Question 9

What is the tympanic membrane connected to?

Answer 9

Surrounding temporal bone by a fibrocartilaginous ring

Question 10

How is the malleus attached to the tympanic membrane?

Answer 10

The handle of malleus attaches at the umbro

Continues superiorly and it has a lateral process of malleus at its highest point

Question 11

What are the parts of the membrane moving away from the tympanic membrane called?

Answer 11

Anterior and posterior malleolar folds

Question 12

What is an auricular haematoma?

Answer 12

When blood collects between cartilage and overlying perichondrium usually as a exult of trauma

Question 13

What can an auricular haematoma lead to and how?

Answer 13

Accumulation of blood disrupts the vascular blood supply to the cartilage of the pinna so if not drained quickly, can get a cauliflower ear

Question 14

What can perforate the tympanic membrane?

Answer 14

Trauma or infection
Otitis media causes pus and fluid to build up causing an increase in pressure so that is eventually ruptures
Membrane normally heals itself, but may require surgery

Question 15

Function of the auricle?

Answer 15

Captures and transmits sound to the external acoustic meatus

Question 16

Which bone does the middle ear lie within?

Answer 16

The temporal bone

Question 17

Where does the middle ear extend from and to?

Answer 17

From the tympanic membrane to the lateral wall of the internal ear

Question 18

Purpose of the middle ear?

Answer 18

Transmit vibrations from the tympanic membrane to the inner ear via three bones

Question 19

Sections of the middle ear?

Answer 19

Tympanic cavity - medial to the tympanic membrane which contains the majority of bones of the middle ear
Epitympanic recess - superiorly, near mastoid air cells

Question 20

Borders of the middle ear?

Answer 20

Visualised as a rectangular box

Roof: thin bone from petrous part of temporal bone.

Floor: ‘jugular wall’. Thin layer of bone separates it from internal jugular

Lateral: tympanic membrane and epitympanic recess

Medial: lateral wall of inner ear

Anterior: thin bony plate with two openings for the auditory tube and tensor tympani muscle. Separates mid ear from internal carotid

Posterior: aka mastoid wall. A bony partition between the tympanic cavity and mastoid air cells. Hole in the partition superiorly allowing communication called the aditus to the mastoid antrum

Question 21

What does the roof separate the middle ear from?

Answer 21

Middle cranial fossa

Question 22

What makes a bulge in the medial wall of the inner ear?

Answer 22

Facial nerve

Question 23

Names of the auditory ossicles?

Answer 23

Malleus
Incus
Stapes

Question 24

What do they connect?

Answer 24

Tympanic membrane to the oval window of the internal ear

Question 25

Where does the head of the malleus lie?

Answer 25

Epitympanic recess where it articulates with the incus

Question 26

What does the incus consist of and what does it articulate with?

Answer 26

Body and two limbs Body articulates with malleus Short limb attaches to posterior wall Long limb to the stapes

Question 27

Shape of the stapes? Articulations?

Answer 27

Stirrup shaped - head, two limbs and a base Head with incus Base to oval window

Question 28

What are the muscles called in the middle ear?

Answer 28

Tensor tympani and stapedius

Question 29

Function of the muscles of the middle ear?

Answer 29

Contract in response to loud noise, inhibiting vibrations of the bones Reduces transmission of sound to the inner ear Called the acoustic reflex

Question 30

Attachments of the muscles?

Answer 30

Tensor tympani: from auditory tube to handle of malleus, pulls it medially Stapedius: attaches to stapes

Question 31

Innervation of the muscles?

Answer 31

Tensor tympani - branch of mandibular nerve | Stapedius - facial nerve

Question 32

Where are the mastoid air cells located? What are they?

Answer 32

Posterior to the epitympanic recess Collection of air-filled spaces in the mastoid process of the temporal bone Contained within a cavity called the mastoid antrum

Question 33

Function of the mastoid air cells?

Answer 33

Act as a buffer system - release air into the tympanic cavity when pressure is too low

Question 34

How do the mastoid air cells communicate with the middle ear?

Answer 34

Aditus to middle antrum

Question 35

What two things does the Eustachian tube connect?

Answer 35

Middle ear to the nasopharynx

Question 36

Function of the Eustachian tube?

Answer 36

Equalises pressure of middle ear to that of the external auditory meatus

Question 37

What is cholesteatoma?

Answer 37

Growth of stratified squamous epithelium in the middle ear | Can be congenital or acquired

Question 38

What problems can cholesteatoma cause?

Answer 38

Damage bones of middle ear due to increase pressure Releases osteolytic enzymes Patients present with hearing loss and sometimes facial nerve palsy

Question 39

How to treat cholesteatoma?

Answer 39

Surgery to remove it

Question 40

What is mastoiditis?

Answer 40

Otitis media can spread to the mastoid air cells, as its a good site for pathogenic replication

Question 41

Complications of mastoiditis?

Answer 41

Mastoid process gets infected and can spread to middle cranial fossa causing meningitis

Question 42

How is mastoiditis treated?

Answer 42

Pus is drained from air cells, careful of nearby facial nerve

Question 43

What is glue ear?

Answer 43

Otitis media with effusion

Question 44

How does otitis media with effusion arise?

Answer 44

Arises from persistent dysfunction of auditory tube If tube is unable to equalise middle ear pressure (blockage, inflammation, genetic mutation), a negative pressure develops inside the middle ear which draws out transudate from the mucosa of the middle ear Creates an environment suitable for pathogens to replicate and cause infection

Question 45

How does the ear drum appear in glue ear?

Answer 45

Inverted, fluid visible

Question 46

Why are children more prone to infection?

Answer 46

Eustachian tube is shorter and more horizontal