The Ear

Question 1

From the outside inwards, name the different ear structures.

Answer 1

Auricle/pinna -> external acoustic meatus (EAM) -> tympanic membrane (ear drum) -> middle ear -> inner ear -> internal acoustic meatus (IAM) -> CN VIII (vestibulocochlear nerve of brainstem) -> intracranial cavity

Question 2

What structures come off of the middle ear?

Answer 2

The auditory tube (also called the Eustachian or pharyngotympanic tube) which leads down to nasopharynx

Question 3

What is the ear?

Answer 3

Organ of hearing, balance + proprioception

Part of upper respiratory tract with direct relations to the nasal cavity + paranasal sinuses

Question 4

What bone is the inner structures of the ear embedded within?

Answer 4

Temporal bone

Question 5

The external ear takes in sound i.e. ___ __ and the inner ear converts it into __ __ so your brain can interpret it.

Answer 5

Mechanical signal

Electric signal

Question 6

What are the three divisions of the ear?

Answer 6

External ear
Inner ear
Middle ear

Question 7

What is the sensory innervation of the pinna, EAM + tympanic membrane? What does this tell you about referred pain?

Answer 7

From multiple cranial + somatic nerves (C2 + 3 & CN Vc, VII + X)

Referred pain to ear can be from:
Mandible + mandibular teeth (CN Vc)
Temporomandibular joint (CN Vc)
Laryngopharynx (CN X)
Cardiac (CN X)

Question 8

What forms the auricle/pinna and what is its main function?

Answer 8

Formed of elastic cartilage covered with skin + a fleshy lobule

Captures soundwaves directing them into the ear (most effective from inferior-superior/anterior direction)

Question 9

What is the innervation of the auricle/pinna?

Answer 9

Helix, antihelix, concha + lobule = C2 + C3

Tragus + antitragus = CN Vc, CNVII + CN X

Question 10

Infection in the auricle/pinna can result in what?

Answer 10

Abscess formation + spread to local node groups

Question 11

What is the EAM formed of? What is its sensory innervation?

Answer 11

Lateral part is cartilaginous whilst bony part is medial

S- shaped (horizontal in child) anteroinferiorly angled passage 2-3 cm long

Modified sweat glands that produce cerumen (wax) inside

Sensory innervation by CN Vc + CN X

Question 12

What is an inflamed EAM called?

Answer 12

Otitis externa (sometimes called swimmers ear if due to chlorine for e.g.)

Question 13

How do you examine the EAM?

Answer 13

In adult: Pull pinna posterior + superior in order to straighten it out to examine it

In child: Pull pinna posterior + inferior in order to straighten it out to examine it (disproportionate different bone structure)

Question 14

Describe the TM.

Answer 14

Pink thin structure between EAM + middle ear that should reflect a concave of light pointing anterior + inferior (right side)

Handle of malleus is first middle ear ossicle that points posterior + inferior -leads up to flaccid part + down to umbo

Tense + flaccid part for vibration due to sound waves

Question 15

What is the chorda tympani? How can it go wrong?

Answer 15

Nerve in upper 1/3 of TM but does nothing here, it travels through middle ear + up to tongue conveying taste to anterior 2/3rds of tongue

TM rupture can damage it resulting in loss of taste on anterior 2/3rd of ipsilateral tongue

Question 16

What can pathology of the TM cause?

Answer 16

Increased concavity, bulging convexity or visible red inflammation + green suppuration -> rupture will provide relief (along with temporary hearing loss)

Question 17

What are the 3 layers of the TM? What is their sensory innervation?

Answer 17

Outside layer = hairless skin (innervated by CN Vc + X)
Middle layer = mesoderm (innervated by CN Vc + X)
Inside layer: respiratory mucosa (innervation by CN IX)

Question 18

What is the pain referral of the TM?

Answer 18

Skin + mesoderm layer refer pain from/to mandible + mandibular teeth, temporomandibular joint, laryngopharynx, larynx + cardiac

Inside layer refer pain from/to pharynx (as innervated by glossopharyngeal nerve)

Question 19

If something is made of respiratory mucosa, what does this mean for it?

Answer 19

It produces mucus so must drain somewhere

Question 20

What cranial nerve carries sensory from all portions of the pharynx, middle ear, auditory tube + inner side of TM?

Answer 20

CN IX

Question 21

What is the sensory innervation of the nasopharynx, oropharynx + laryngopharynx?

Answer 21

Naso: CN Vb + IX
Oro: CN IX
Laryngo: CN IX + X

Question 22

What are the functions of the middle ear?

Answer 22

Space lined with respiratory mucosa with bones in it: maleus, incus + stapes

Ossicles link TM to oval window - in space lined with respiratory mucosa

Bones amplify signal from large TM to small oval window

Question 23

What can occur if the middle ear ossicles are damaged or if there is middle ear disease?

Answer 23

Mobile synovial joints located between ossicles can dislocate or be subject to disease (but ligaments prevent dislocation) -> conductive hearing loss

Question 24

What are the 2 muscles of the middle ear that control the oscillatory range of the ossicles?

Answer 24

1. Tensor tympani: originate in bony canal above pharyngotympanic tube + insert into neck of malleus - pulls TM medially (taut) reducing amplitude of vibrations (strong noise) (supplied by nerve CN Vc)
2. Stapedius: passes from pyramidal eminence to stapes - pulls stapes + limits range of movement in response to large vibrations (loud noise) (supplied by nerve CN VII)

Question 25

What might happen with a CN VII facial nerve palsy?

Answer 25

Facial nerve passes through inner ear + controls the stapedius muscle of middle ear so this muscle may become paralysed causing hyperacusis (exceptional sensitivity to loud noises which is physically painful)

Question 26

What are the 6 walls of the middle ear space?

Answer 26

``` Anterior wall (carotid) Superior wall (tegmen tympani) Lateral wall (membranous) Inferior wall (jugular) Medial wall (labarynthine) Posterior wall (mastoid) (named after their close relations meaning spread of clinical conditions can occur to all kinds of vessels, nerves + inner ear) ```

Question 27

Give some examples of clinical conditions occurring from middle ear infections (otitis media).

Answer 27

Affect vestibular system causing dizziness Spread to mastoid air cells causing mastoiditis Affect cranial facial nerve VII resulting in ipsilateral facial palsy

Question 28

What is the only route for air + fluid to escape from the middle ear? What can happen if this gets blocked?

Answer 28

Pharyngotympanic tube which opens into nasopharynx so blockage of the tube prevents drainage of middle ear epithelial secretions + pressure equalization

Question 29

Describe the pharyngotympanic tube.

Answer 29

1/3rd bone + 2/3 cartilage trumpet-shaped structure lined with respiratory mucosa with opening surrounded by tubal tonsil tissue Normally closed but opened when swallowing by tensor veli palatine, levator palatine + salpingopharyngeus

Question 30

What is acute infective (suppurative) otitis media?

Answer 30

Often result of infection spread from nasopharynx to middle ear via pharyngotympanic tube Pus accumulates in middle ear = pain + swelling of TM (perforation provides relief)

Question 31

What is chronic secretory otitis media (glue ear)?

Answer 31

Persistent build up of mucoid fluid due to blockage of pharyngotympanic tube Causes conductive hearing loss + speech/language development problems in young

Question 32

What 4 structures are involved in the formation of the ear in embryology? What structures do they form + what is their sensory innervation?

Answer 32

1. 1st pharyngeal arch: tensor tympani, tensor veli palatini, malleus + incus (CN V) 2. 2nd pharyngeal arch: facial expression muscles, stapedius + stapes (CN VII) 3. 1st cleft: EAM 4. 1st pouch: tubotypanic recess (tympanic cavity, mastoid antrum + auditory tube)

Question 33

What embryological structures form the TM?

Answer 33

Ectoderm & endoderm 1st pouch + 1st cleft

Question 34

What can occur as a result of the auricular sinus?

Answer 34

An additional EAM (small/non-functional) can develop in front of pinna Auricular sinus can be quiescent or become infection, form cysts or discharge

Question 35

When you examine the ear, what parts would you want to consider?

Answer 35

The ear + EAM for blood, blockage, poly, vesicles (Ramsay-Hunt; latent chicken-pox virus), infection + secretions The mastoid process as, well as the outside of ear (behind ear) Test hearing in both ears using a 256 Hz tuning fork (bedside testing-whisper tests)

Question 36

Explain the Rinne test of the cochlear portion of CN VIII (vestibulocochlear nerve in brainstem).

Answer 36

Tuning fork on mastoid till sound stops then hold in air by EAM; - Air conduction should be better than bone conduction (Rinne +ve) - No note at EAM = conduction deafness (Rinne -ve)

Question 37

Explain the Weber test of the cochlear portion of CN VIII (vestibulocochlear nervein brainstem).

Answer 37

Tuning fork on forehead + ask where patient hears sound/vibrating + if its louder on one lateral side; - Normally no lateralisation - Sound loudest in affected ear (conduction deafness) - Sound loudest in normal ear (sensorineural deafness)