Clinical anatomy of the ear

Question 1

what are the 2 parts of the temporal bone?

Answer 1

• squamous part

- petrous part

Question 2

what makes up the external ear and whats it function?

Answer 2

• auricle to tympanic membrane
• via external acoustic meatus
• collects and conveys sound waves to tympanic membrane

Question 3

what makes up the middle ear and whats it function?

Answer 3

• tympanic membrane to oval window
• also eustachian tube
• amplifies & conducts sound waves to the internal ear

Question 4

what makes the internal ear and whats it function?

Answer 4

-oval window to internal acoustic meatus
-converts special sensory information-into fluid waves,
then APs,conducts APs to brain

Question 5

what is the external ear made of and whats it’s properties?

Answer 5

• temporal bone
• elastic cartilage
• avascular
• nutrients from skin
• do not use anaesthetic containing adrenaline on external ear

Question 6

what is the ear canal made of?

Answer 6

• 1/3 cratilage

- 2/3 bony and is lined with skin

Question 7

what is the nerve supply to the auricle?

Answer 7

• C2,3
• CN VII
• CN V3
• CN X (look at lecture side 8)

Question 8

what lymph nodes drain the auricle?

Answer 8

• Lateral surface of superior half -parotid lymph nodes
• Cranial surface of superior half-mastoid lymph nodes (and deep cervical)
• Rest of auricle, including lobe- superficial cervical lymph nodes

Question 9

where does the lymph eventually drain to?

Answer 9

deep cervical lymph nodes (in carotid sheath) then into the thoracic duct or right lymphatic duct then into the
venous angle

Question 10

what is the difference between a child’s EAM and an adults?

Answer 10

• childs is short and straight (gently pull auricle posteroinferiorly)
• adults is curved and gently pull auricle posterosuperiorly

Question 11

what are the 4 parts of the ear of the otoscopic examination?

Answer 11

• pars flaccida (thin part of the tympanic membrane superiorly)
• the jumbo
• the cone of light
• pars tensa (thick part of the tympanic membrane posteroinferiorly)

Question 12

what is the general sensory nerve supply to the tympanic membrane?

Answer 12

external surface- mostly CN V3

internal surface- CN IX

Question 13

where does the glossopahrygeal nerve provide sensory innervation to?

Answer 13

middle ear cavity
eustachian tube
nasopharynx
oropharynx
tonsils

Question 14

what is the function of the Eustachian tube ?

Answer 14

connects middle ear cavity to nasopharynx

Question 15

what are the 3 auditory ossicles?

Answer 15

• malleus
• incus
• stapes

Question 16

how do the 3 ossicles articulate to each other?

Answer 16

synovial joints

Question 17

what fits into the base of the stapes?

Answer 17

oval window into internal ear

Question 18

what forms the bony swelling on the medial wall?

Answer 18

Formed by the cochlea of the internal ear

Question 19

what causes mastoiditis?

Answer 19

spread of infection from middle ear cavity

Question 20

what is the aditus?

Answer 20

doorway into the mastoid antrum from the epitympanic recess

Question 21

what does the chord tympani (branch of CN VII) supply?

Answer 21

• taste buds of the anterior 2/3rds of the tongue
• parasympathetic supply to the submandibular & sublingual salivary glands (salivation)

Question 22

what is the role of the right stapedius?

Answer 22

reduces stapes movement to protect the internal ear from excessive noise

Question 23

what course does the facial nerve take through the base of the skull?

Answer 23

• through internal acoustic meatus
• in the facial canal of the petrous temporal bone
• stylomastoid foramen

Question 24

what does the internal ear consist of and whats its function?

Answer 24

• oval window to internal acoustic meatus
• petrous part of temporal bone
• converts special sensory information

Question 25

what are the 2 parts of the CN VIII?

Answer 25

-the cochlear nerve (hearing) - the vestibular nerve (balance)

Question 26

where does the dense otic capsule sit?

Answer 26

in the temporal bone

Question 27

what does the otic capsule contain?

Answer 27

Bony labyrinth - filled with perilymph

Question 28

what is suspended within the perilymph of bony labyrinth?

Answer 28

- membranous labyrinth - communicating sacs and ducts - contains endolymph fluid

Question 29

how many turns does the cochlea have?

Answer 29

2

Question 30

what are the 3 semicircular canals and whats their function?

Answer 30

- anterior - lateral - posterior - associated with balance

Question 31

what is the cochlear duct and what conducts their action potentials?

Answer 31

- a long balloon-like structure within the cochlea filled with endolymph - cochlear nerve

Question 32

what is the semicircular duct and what conducts their action potentials?

Answer 32

- inter-linked balloon-like structures within the semicircular canals filled with endolymph - vestibular nerve

Question 33

what stimulates hair cells?

Answer 33

movement of endolymph

Question 34

what are clusters of hair cells called?

Answer 34

maculae

Question 35

what detects angular movement change?

Answer 35

semicircular ducts

Question 36

what detects linear movement change?

Answer 36

- utricle (horizontal) | - saccule (vertical)

Question 37

what are the steps of sound transmission?

Answer 37

1) Sound waves make tympanic membrane vibrate 2) Vibrations transmitted through ossicles 3) Base of stapes vibrates in oval window 4) Vibration of stapes creates pressure waves in perilymph 5) Hair cells in the cochlea are moved, neurotransmitter is released, APs stimulated and conveyed to brain by cochlear nerve 6) Pressure waves descend and become vibrations again 7) Pressure waves are dampened at the round window

Question 38

where does CN VII and VIII connect with the brainstem?

Answer 38

junctions between the pons and the medulla oblongata

Question 39

what are symptoms associated with pathology at the internal acoustic meatus regarding the CN VII?

Answer 39

- ipsilateral loss of facial expression - ipsilateral loss of taste - dry mouth (reduced ipsilateral salivation) - reduced general sensation in the auricle (immediately posterior to the tragus)

Question 40

what are symptoms associated with pathology at the internal acoustic meatus regarding the CN VIII?

Answer 40

- ipsilateral loss of hearing (cochlear nerve) | - ipsilateral loss of balance (vestibular nerve)