NB 29+30

Question 1

innervation of the auricle

Answer 1

posterior 2/3 = great auricular (C2/C3) and lesser occipital N (C2)

anterior 1/3 = Auriculotemporal nerve (V3)

Question 2

development of the auricle

Answer 2

The ear develops from 6 auricular hillocks
3 from the 1st arch and 3 from the 2nd arch mesenchyme tissue

malformation can lead to auricular sinuses and cysts

Question 3

Pre-auricular sinus

Answer 3

due to incomplete fusion of the primitive tubercles that form the pinna

Question 4

Preauricular pits

Answer 4

Auricular sinuses/pits are usually present anterior to the auricle and considered remnants of the 1st pharyngeal groove.

common! May indicate other congenital defects

Question 5

External acoustic meatus

Answer 5

lateral 1/3 of canal is cartilaginous
medical 2/3 is bony and part of the tympanic portion of temporal bone

innervated by the Auriculotemporal nerve (V3)
a small area is innervated by CN X

Question 6

innervation of the tympanic membrane

Answer 6

external surface auriculotemporal nerve (V3) except for small area by CN VII and CN X

internal surface is by tympanic plexus (CN IX)

Question 7

innervation of the middle ear

Answer 7

glossopharyngeal nerve via the tympanic plexus

Question 8

development of the middle ear

Answer 8

Develops from the distal expanded part of the tubotympanic recess arising from the 1st pharyngeal pouch

Question 9

where do the auditory ossicles develop from

Answer 9

malleus and incus develop from the 1st arch
stapes from the 2nd arch

tensor tympani is the first arch
stapedius is from the second arch

Question 10

development of external ear

Answer 10

Surface ectoderm grows & forms a solid meatal plug which undergoes canalization to form the external auditory meatus

Question 11

development of the tympanic membrane

Answer 11

develops from the 1st pharyngeal membrane

it is derived from all three germ layers

Question 12

chorda tympani nerve

Answer 12

sensory fibers for taste from anterior 2/3 of tongue

parasympathetic (preganglionic) innervation for submandibular and sublingual glands

Question 13

disruption of ossicular chain

Answer 13

conductive hearing loss

Question 14

clinical importance of the stapes

Answer 14

otosclerosis

Question 15

clinical importance of chorda tympani N

Answer 15

reduction of salivation if damaged

Question 16

middle ear boundaries

Answer 16

roof (tegmen tympani) - separates cavity from middle cranial fossa

medial wall - separates cavity from middle ear

anterior wall - separates cavity from carotid canal

floor: base of skull near jugular foramen

lateral wall: mainly tympanic membrane

posterior wall - separates cavity from mastoid air
cells

Question 17

innervation of the inner ear

Answer 17

CN VIII

vestibular nerve - balance
cochlear nerve - hearing

Question 18

development of the inner ear

Answer 18

The otic vesicle, derived from the ectoderm, will give rise to the membranous labyrinth

The cartilaginous otic capsule undergoes ossification to form the bony labyrinth

Question 19

Atresia of EAM

Answer 19

absent external acoustic meatus

failure of the central cells of the meatal plug to canalize

Question 20

middle ear amplification

Answer 20

pressure = force / area

decrease area
increase force

Question 21

what two muscles limit excessive pressure in the middle ear

Answer 21

Contraction of m. tensor tympani and m. stapedius
occurs in response to high intensity sound – attenuation reflex

restricts the movement of the tympanic membrane and makes the ossicles more rigid

does not protect against sudden loud noises

Question 22

outer hair cells and inner hair cells

Answer 22

outer = signal amplification ( K influx / depolarized)
these cells expand when hyperpolarized and compress when depolarized

inner = majority of signal transduction (no K influx / hyperpolarize)

Question 23

lesions to lead to unilateral hearing loss

Answer 23

cochlear nuclei
ear
CN VIII

Question 24

Area 41 and 42

Answer 24

primary auditory cortex

Question 25

Vestibular Schwannoma

Answer 25

a benign tumor originating from the Schwann cells of the vestibular division of CN VIII

this tumor compresses the nerve within the internal auditory meatus

symptoms are sensorineural hearing loss and tinnitus

Question 26

Meniere’s Disease

Answer 26

repeated episodes of vertigo, can have tinnitus and progressive sensorineural hearing loss

due to distortion of the membranous labyrinth that results in an over production of endolymph

Question 27

Weber’s test

Answer 27

testing auditory functioning

normal:
hear the the tuning fork the same on each side

abnormal:
the sound is louder on one side compared to the other

Question 28

how to interpret abnormal weber’s test

Answer 28

In sensorineural hearing loss:
The sound lateralizes to the unaffected side

Conductive hearing loss:
The sound will lateralize to the affected side

lateralize = louder

Question 29

Rinne’s test

Answer 29

1. bone conduction
   the stem of the turning fork is put on mastoid process
   (bone to inner ear)
   patient must say when they no longer hear it
2. air conduction
   bring the tuning fork to the ear
   (do you hear sound again? when dont you hear it)

Question 30

normal and abnormal Rinne’s test

Answer 30

normal:
air conduction sound should be better than bone conduction AC > BC

abnormal:
BC > AC
conductive hearing loss

AC > BC
but times of hearing vibration are different
Sensorineural hearing loss

AC = BC = 0
total deafness

Question 31

Weber’s test lateralizes to the left

Rinne’s test is BC > AC

Answer 31

conductive hearing loss on the left

Question 32

Weber’s test lateralizes to the left

Rinne’s test AC > BC ( but reduced times )

Answer 32

sensorineural hearing loss on the right