11. Functional Anatomy And Disorders Of The Ear

Question 1

Within which bone of the skull are the parts of the ear found?

Answer 1

Petrous part of the temporal bone.

Question 2

What are the 3 parts of the ear?

Answer 2

External, middle and inner ear.

Question 3

What is the function of the external ear?

Answer 3

Collects, transmits and focuses sound waves onto the tympanic membrane.

Question 4

What 3 structures comprise the external ear?

Answer 4

Pinna.
External auditory meatus.
Lateral surface of tympanic membrane.

Question 5

What does the pinna comprise of?

Answer 5

Cartilage, skin and fatty tissue.

Question 6

What is Ramsey-Hunt syndrome?

Answer 6

Shingles (reactivation of the varicella zoster virus) causing shingles of the pinna. Also causes a facial nerve palsy (weakness of one side of the face).

Question 7

What happens in a pinna haematoma?

Answer 7

Accumulation of blood between the cartilage and pericardium of the pinnacle, secondary to blunt injury.

Question 8

How should a pinna haemotoma be treated?

Answer 8

Prompt drainage, take measures to prevent re-accumulation and re-apposition of the two layers is necessary.

Question 9

What deformity is can an untreated or poorly treated pinna haematoma cause?

Answer 9

Cauliflower deformity of the ear due to fibrosis and new asymmetrical cartilage development.

Question 10

Why does the ear need to be pulled up and back to straighten when examining?

Answer 10

The external acoustic meatus is sigmoid shape.

Question 11

In which portion of the external acoustic meatus are there hairs and is wax produced?

Answer 11

Cartilaginous (outer 1/3).

Question 12

What is the purpose of the arrangement of hairs and production of wax in the external acoustic meatus?

Answer 12

Prevent objects entering the deep ear canal.

Aid in desquamation and skin migration out of the canal.

Question 13

How long is the external acoustic meatus?

Answer 13

2.5 cm.

Question 14

What is otitis externa?

Answer 14

Inflammation of the external acoustic meatus eg eczema and swimmers (water in ears, bacteria breed).

Question 15

What 2 things can cause perforation of the tympanic membrane?

Answer 15

Perforation by an object.

Increase in pressure due to infection eg build up of pus and discharge.

Question 16

What can be seen at the tympanic membrane secondary to otitis media (middle ear infection)?

Answer 16

Bulging.

Question 17

What is the middle ear comprised of?

Answer 17

The ossicles and an air filled cavity.

Question 18

What is the function of the middle ear?

Answer 18

Is an air filled cavity between the tympanic membrane and the inner ear, which contains 3 ossicles which amplify vibration from the tympanic membrane to the cochlea via the oval window.

Question 19

What are the 3 ossicles?

Answer 19

Malleus, incus, stapes.

Question 20

What is the acoustic reflex?

Answer 20

Tensor tympani and stapedius muscles contract in response to a potentially excessive vibration due to loud noise, decreasing the transmission of vibrational energy to the cochlea, where it is converted into electrical impulses to be processed by the brain.

Question 21

What is otosclerosis?

Answer 21

Fusion of the ossicles at articulations, in particular between the base plate of the stapes and oval window. This means sound vibrations cannot be transmitted, causing deafness.

Question 22

What is the function of the pharyngotympanic tube (eustachian tube)?

Answer 22

Equilibrates pressure of the middle ear (mucous membrane of the middle ear continuously reabsorbs air in the middle ear, causing negative pressure).
Allows for ventilation of and drainage of mucus from the middle ear.

Question 23

What causes otitis media with effusion (glue ear) and how does this affect hearing?

Answer 23

Build up of fluid and negative pressure in the middle ear due to Eustachian tube dysfunction. (Is not an infection).
Decreases mobility of the tympanic membrane and ossicles affecting hearing.

Question 24

What is the treatment for otitis media with effusion (glue ear)?

Answer 24

Most resolve spontaneously in 2-3 months, it some may persist, and so require grommets to ventilate the middle ear.

Question 25

What can predispose the middle ear to infection?

Answer 25

East ACh Ian tube dysfunction.

Question 26

How does the tympanic membrane look in otitis media with effusion (glue ear)?

Answer 26

Retracted and tympanic membrane looks straw coloured.

Question 27

What causes acute otitis media?

Answer 27

An acute middle ear infection.

Question 28

Acute otitis media is more common in infants and children rather than in adults. Why is this anatomically?

Answer 28

The pharyngotympanic tube is shorter and more horizontal in infants, to it is easier to the passage of infection from the nasopharynx to the middle ear. And the tube can block more easily, compromising ventilation and drainage of the middle ear, increasing risk of middle ear infection.

Question 29

What symptoms does acute otitis media cause?

Answer 29

Otalgia (ear pain which may lead to infants pulling or tugging at the ear). Other non-specific symptoms eg temperature. Red, bulging tympanic membrane and loss of normal landmarks.

Question 30

Name 3 complication of acute otitis media.

Answer 30

Tympanic membrane perforation. Facial nerve involvement. Rarer but potentially life-threatening complications: Mastoiditis. Intracranial complications (meningitis, sigmoid sinus thrombosis, brain abscess).

Question 31

What is mastoiditis?

Answer 31

Infection spreading from the middle ear cavity into the mastoid air cells of the mastoid bone.

Question 32

How does the middle ear cavity communicate with the mastoid air cells?

Answer 32

Via the mastoid antrum

Question 33

What 2 signs are seen in mastoiditis?

Answer 33

Swollen area behind ear. | Ear pushed forward.

Question 34

What nerve may be involved in pathology involving the middle ear and why?

Answer 34

Facial nerve, as it and one of its branches, the chora tympani, runs through the middle ear cavity.

Question 35

What is a cholesteatoma?

Answer 35

Abnormal skin growth (sac or cyst of skin cells) growing into the middle ear, behind the tympanic membrane.

Question 36

What signs/symptoms does a cholesteatoma cause?

Answer 36

Painless, smell otorrhea (ear discharge), with or without hearing loss. Can potentially cause more serious neurological complications.

Question 37

What is a cholesteatoma usually secondary to?

Answer 37

Chronic Eustachian tube dysfunction or chronic/recurring ear infections.

Question 38

What does the inner ear comprise of?

Answer 38

The vestibular apparatus and cochlea.

Question 39

What is the function of the inner ear?

Answer 39

The cochlear converts vibration into an electrical signal (action potential) which is perceived as sound. The vestibular apparatus is involved in maintaining our sense of position and balance.

Question 40

How does the cochlear generate action potentials in the CN VIII?

Answer 40

Movements at the oval window sets up movements of the fluid in the cochlear. The waves of fluid cause movement of special sensory cells within the cochlear duct which generate action potentials in the CN VIII.

Question 41

What is the name of the special sensory cells int eh cochlea duct?

Answer 41

Stereocilia.

Question 42

Where does the CN VIII carry signals from the cochlear to?

Answer 42

The primary auditory cortex.

Question 43

What structures is the vestibular apparatus made of? And what are they?

Answer 43

Semicircular ducts, the saccule and utricle. | Are a fluid filled series of channels and sacs that respond to position and rotation and maintain our sense of balance.

Question 44

Name 2 diseases of the inner ear caused by pathology involving the vestibular apparatus.

Answer 44

Ménière's disease. Benign paroxysmal positional vertigo. Labrynthitis.

Question 45

Give 3 symptoms that can occur as a result of a disease involving the vestibular apparatus

Answer 45

Vertigo. Hearing loss and tinnitus. Nystagmus.

Question 46

Where is there pathology in conductive hearing loss and give 3 causes of conductive hearing loss.

Answer 46

External and middle ear. | Wax, otitis media, glue ear, otosclerosis.

Question 47

Where is the pathology in sensorineural hearing loss and give 3 causes of sensorineural hearing loss.

Answer 47

Inner ear structures or CN VIII. | Presbyacusis, Ménière's disease, acoustic neuroma, ototoxic medication.

Question 48

How do you perform a Rinne's test?

Answer 48

Ring tuning form over mastoid process and then in front of ear. Which is louder, bone or air conduction?

Question 49

How do you perform a Weber's test?

Answer 49

Ring tuning fork and place in centre on top of head. Same or louder in one ear?

Question 50

In sensorineural hearing loss, when will a Rinne's and Weber's test be louder?

Answer 50

Rinne's - louder in air than bone. | Weber's - louder in normal ear.

Question 51

In conductive hearing loss, when will a Rinne's and Weber's test be louder?

Answer 51

Rinne's - louder in bone than air. | Weber' - louder in affected ear.