Ear - Anatomy & Physiology

Question 1

what is Jacobsons nerve and what does it supply?

Answer 1

Tympanic branch of the glossopharyngeal nerve CN IX

- sensation to middle ear

Question 2

What is arnolds nerve and what does it supply?

Answer 2

Auricular branch of the vagus nerve CN X

- sensation to posterior half of the external auditory canal

Question 3

what part of the ear does the vagus nerve supply?

Answer 3

posterior half of the EAC

Question 4

what nerve supplies the pinna?

Answer 4

upper half = CN V3

lower half = greater auricular nerve (C2/C3)

Question 5

what part of the ear does the facial nerve supply?

Answer 5

the anterior half of EAC

Question 6

what nerve supplies the inner ear?

Answer 6

vestibulocohlear nerve (CN VIII)

Question 7

WHAT IS THE LENTGH OF THE EXTERNAL EAR CANAL?

Answer 7

4cm

Question 8

what is the medial and lateral 1/3rd of the EAC made of?

Answer 8

medial third made of skin and bone

lateral third made of skin and cartilage

Question 9

what does the skin contain in the lateral 1/3rd of the EAC?

Answer 9

ceruminous and sebaceous glands which produce wax

Question 10

what are 2 characteristics of the medial 1/3rd of the EAC?

Answer 10

no hairs or cilia

doesn’t produce wax (don’t have ceruminous or sebaceous glands in the skin)

Question 11

where does the skin of the EAC grow from?

Answer 11

grows from the umbo of the tympani membrane outwards

Question 12

what type of skin and what type of cartilage is found in the EAC?

Answer 12

Stratified keratinised epithelium

Elastic cartilage

Question 13

why does minimal hearing loss occur with damage to the EAC?

Answer 13

the pinna isn’t good at sound localisation so if there is wax or disruption this can cause minimal hearing loss

Question 14

what are the 3 layers of the tympanic membrane?

Answer 14

outer layer - continuous with skin of EAC
middle - fibrous layer
inner layer = respiratory epithelium (ciliated columnar epithelium with goblet cells)

Question 15

what plays an important role in sound conduction?

Answer 15

ear ossicles found in the middle ear

Question 16

what does the ossicles attach to?

Answer 16

connects to mastoid system via audits

connects to nasopharynx via eustachian tube

Question 17

the middle ear receives sensation from the tympanic branch of glossopharyngeal nerve but what nerve runs through the middle ear?

Answer 17

chords tympani - branch of facial nerve

Question 18

what are important relations of the inner ear?

Answer 18

middle cranial fossa
internal carotid artery
sigmoid sinus and internal jugular vein

Question 19

apart from running through the middle ear, what else does the chord tympani supply?

Answer 19

taste to the anterior 2/3rds of tongue

Question 20

what is cholesteatoma?

Answer 20

skin in the middle ear
keratinised squamous epithelium in the wrong place
the skin grows and becomes destructive

Question 21

what are the collection of tubes and chambers within the inner ear known as?

Answer 21

labyrinth

Question 22

what type of fluid is within the membraneous labyrinth?

Answer 22

perilymph and endolymph

Question 23

what part of the inner ear is the the hearing organ?

Answer 23

organ of corti

Question 24

what forms the peripheral vestibule aparatus in the inner ear?

Answer 24

semi circular canals
utricle
sacculae

Question 25

what is the function of the semi circular canals in the inner ear?

Answer 25

detects head movement | vestibulo-occula reflex allows us to focus on an object when our head is moving

Question 26

what is the function of the utricle and saccule in the inner ear?

Answer 26

utricle = detects linear movement in the horizontal plane | saccule - detects linear movement in the vertical plane

Question 27

describe how we hear.

Answer 27

middle ear traduces vibration into nerve impulses the foot of stapes vibrates in the oval window which causes a pressure wave through the fluid in the cochlea the pressure wave is detected by hairs in the organ of corti which is then transmitted to the brain stem via vestibule-cochlear nerve VIII

Question 28

Otalgia can be secondary to other conditions which cause damage to what nerves which affect the ear?

Answer 28

C2/C3 CN X - vagus CN V - trigeminal CN XI - glossopharyngeal

Question 29

what does the auricular branch of the vagus nerve supply?

Answer 29

the lower part of the pinna | the posterior part of the EAC

Question 30

what tests can be carried out for assessing hearing ?

Answer 30

clinical testing - hearing threshold test tuning fork test - webers & rinne audiometry - pure tone audiometry, visual reinforcement, play audiometry, tymapanometry

Question 31

how does tympanometry work>

Answer 31

detected pressure within the middle ear pushes air pressure into the ear canal which causes the tympanic membrane to move back and forth it measures the mobility of the tympanic membrane which is put into a graph called a typanogram

Question 32

what can a tympanometry detect?

Answer 32

wax blocking the ear fluid in the middle ear perforation of the tympanic membrane

Question 33

how does are tone audiometry work?

Answer 33

pure tone air conduction test measures the minimum tone a person can hear at selected pitches (frequencies) from low to high earphones are worn so information can be obtained from each ear

Question 34

how is hearing loss managed?

Answer 34

surgery of outer and middle ear sound amplification (hearing aids) direct stimulus of cochlear nerve (cochlear implant)

Question 35

what 3 systems does humans use for balance?

Answer 35

vision vestibular (otolith organs in inner ear) proprioception (CNS- cerebellum, cerebral cortex and brain stem)

Question 36

what is the main clinical condition of the inner ear which causes imbalance?

Answer 36

benign paroxysmal positional dysfunction (BPPD)

Question 37

what commonly causes imbalance? (not from the inner ear)

Answer 37

migraines

Question 38

what is responsible for imbalance in people with BPPD?

Answer 38

calcium carbonate outwit the utricle into the semicircular canal

Question 39

where does the cells which detect head movement and stabilisation lie within the inner ear?

Answer 39

the ampulla of the semi circular canals

Question 40

where is higher frequency picked up and where is lower frequency picked up within the ear?

Answer 40

higher picked up more external | lower picked up more internal

Question 41

what type of lymph is the cochlear filled with?

Answer 41

endolymph

Question 42

why is the facial nerve important for surgeons when operating on or near the middle ear?

Answer 42

they have to be aware of the facial nerve and its 6 branches as it passes through the middle ear a branch a branch - chord tympani supplies taste to anterior 2/3rds of the tongue provides motor supply to muscles of facial expression

Question 43

what helps to stabilise the pressure within the middle ear and how?

Answer 43

eustachian tube - opens during swallowing and yawning to equalise pressure mastoid air system via audits- releases air into middle ear when pressure gets too low

Question 44

what can chronic dysfunction of the eustachian tube lead to?

Answer 44

negative pressure which causes retraction of the tympanic membrane leading to otitis media with effusion