Ear

Question 1

Describe the divisions of the ear

Answer 1

Outer
- auricle, external auditory meatus and external surface of tympanic membrane

Middle
- Internal surface of tympanic membrane, tympanic cavity, ossicles, pharyngotympanic tube

Inner
- auditory/vestibular apparatus, internal auditory meatus, CN VIII, ovala and round window

Question 2

within which bone is the inner ear found?

Answer 2

Petrous temporal bone

Question 3

Where does lymph from the auricle drain?

Answer 3

Parotid and cervical nodes

Question 4

What supplies the auricle with blood?

Answer 4

Branches of ECA

• Superficial temporal
• Anterior auricular
• Posterior auricular
• Perforating branches

Question 5

Describe the innervation of the auricle?

Answer 5

Facial 
 - Helix, lobe, behind ear 
CN IX/X
 - Towards ear cavity 
CNV3 Auriculotemporal 
 - Anterior to ear

Question 6

What is the lateral 3rd of the EAM?

Answer 6

Elastic cartilage

Question 7

What is the medial 2/3rd EAM?

Answer 7

Bone lined with stratified squamous epithelium

Question 8

Where does the EAM run?

Answer 8

From opening in auricle to petrous temporal bone and tympanic membrane

Question 9

Describe the innervation of EAM ?

Answer 9

Mainly auriculotemporal CNV3

some branches of CN VII, X

Question 10

What epithelium is on the outer surface of the tympanic membrane?

Answer 10

Stratified squamous

Question 11

What structure runs across the tympanic membrane?

Answer 11

Chorda tympani

Question 12

Describe the innervation of the tympanic membrane

Answer 12

Lateral surface = CNV3, auricular branch of CN X

Medial surface = tympanic branches of CN IX

Question 13

Name the ossicles.

What joint type exists between each?

Answer 13

Malleus
Incus
Stapes

Synovial plane joints

Question 14

Origin, insertion, action and innervation of tensor tympani

Answer 14

O - Wall of auditory tube
I - Handle of malleus
A - Tenses TM
I - CNV3

Question 15

Origin, insertion, action and innervation of stapedius

Answer 15

O - Pyramid of middle ear
I - Neck of stapes
A - Pulls footplate of stapes laterally
I - CN VII

Question 16

What gives sensory innervation to tympanic cavity?

Answer 16

CN IX

Question 17

What does chorda tympani supply?

Answer 17

Parasympathetic supply to sublingual and sub-mandibular salivary glands

Special sensory - Taste to anterior 2/3rds tongue

Question 18

Describe the lining of the medial and lateral sections of auditory tube

Answer 18

Lateral 1.2cm = bony canal

Medial 2.5xm = cartilaginous and membranous

Question 19

Is the auditory tube usually open?

Answer 19

Closed, opened by contraction of tensor veli palatini

Question 20

What is the sensory innervation to the auditory tube?

Answer 20

CN IX

Question 21

Blood supply to middle ear?

Answer 21

Ant tympanic artery from 1st part maxillary

also contributions from ascending pharyngeal, middle meningeal and posterior auricular arteries

Question 22

Name the bony labyrinths

Answer 22

Cochlea
SCC
Vestibule

Question 23

Where are the labyrinths found?

Answer 23

Inner ear

Question 24

What is the membranous labyrinth surround by and what does it contain?

Answer 24

surrounded by perilymph

contains endolymph

conduct sound vibrations and response to changes in acceleration/movement

Question 25

Explain how sound passes to the cochlea

Answer 25

vibration from footplate of stapes to oval window, vibration at oval window causes a wave of movement to pass into perilymph of Scala vestibule which ascends to top of cochlea then back down to round window.

Round window vibrates into middle ear and sound dissipates

Question 26

Which structure detects movement and balance?

Answer 26

SCC

utricle and saccule

Question 27

What is the crust ampullaris and where is it found?

Answer 27

equilibrium receptor that response to rotational movement of the head

found in the ampulla

Question 28

Whta is within the vestibule?

Answer 28

utricle and saccule

Maculae - respond to change in head position

Question 29

Describe the arterial supply to the inner ear

Answer 29

Branches of internal auditory/labrynthine artery

• Common cochlear artery
• Vestibular artery

Question 30

What is the internal auditory artery a branch of?

Answer 30

Anteroiferior cerebellar (>80%)

Occasionally basilar