Lecture 2 - Ear

Question 1

*** What nerves are the auricle and external acoustic meatus and tympanic membrane innovated by?

Answer 1

Auricle - superficially - cervical plexus, V3, deeper parts - X and VII

External acoustic meatus - V3, X, VII

Tympanic membrane - outer surface by V3, X, VII, IX

If there is infection - then can get pain in neck ect. - where nerve is

The auricle and external acoustic meatus have differential innervation. The auricle is innervated by the lesser occipital nerve, the auriculotemporal branch of the mandibular nerve and the great auricular nerve. Consequently an infection on the auricle can lead to pain being referred to the whole head.
The vagus and facial nerves innervate some regions of the inner auricle.

Question 2

Problems with getting middle ear infection?

Answer 2

can drain to the skull, also can drain into the mastoid process causing mastoiditis via the mastoid atrum - anterior wall, (can also go to mastoid cells in cranium via the middle cranial fossa leading to meningitis)

(medical emergency - dont want infection to go to skull)

Question 3

What does the tegmental wall separate the middle ear from?

Answer 3

From the middle cranial fossa (is the roof)

Question 4

What is floor of middle ear made up of? what does it separate?
-what goes thru it?

Answer 4

Jugular wall (floor) - separates middle ear from internal jugular vien. Also has a branch of the IX nerve entering the middle ear which joins the tympanic membrane

Question 5

Problem with removing tympanic membrane?

Answer 5

Chorda Tympani nerve runs right behind this - supplies taste so if this is damaged then cannot taste anything must be careful.

Question 6

what can you see in a normal tympanic membrane?

Answer 6

Normal - Can see cone of light, handle of malleolus, lateral process, and should be clear

(umbo, posterior and anterior mediollar fold, pars flacida - also parts of ear)

Of there is an infection, the lateral process and the umbo are very prominent - something wrong with middle ear as eustacian tube which goes to back of nose cnat equalise the pressure so it is pulling the tympanic membrane and then can see the processes more prominently
-ear would look like pars flacida as it would all be fuzzy

Question 7

Medial wall (could ask exam Q on this)
-What is in here?

Answer 7

Promontory (protrusion of cholcea) - covered by mucous membrane, cintains tympanic plexus, (IX, caroticotympanc nerves) - because choncha is behind this (needs nerve supply)

Oval and round windows

Lesser petrosal nerve - leaves middle ear and runs along the middle cranial fossa and exits to reach the otic ganglion carrying preganglionic parasympathetic fibers.

Question 8

Pharyngotympanic tube (eustachian tube) significance

Answer 8

Babies can get this

• Need to look at tympanic membrane
• tube is made up of a bony part and cartilagenous part
• soft palate - pulls on the opening of the eustachian tube (these muscels try and balance the pressure within the tube and middle ear)
• if tube is blocked, cannot get pressurized and air in
• if block - then bacteria can start growing and can block it
• can destroy structures in ear and cause death

Question 9

What is the blood supply to the middle ear?

Answer 9

Branches from external carotid artery supply external aucostic meatus and middle ear
-nerve supply - tympanic plexus

Question 10

What nerves form the tympanic plexus

-where do these nerves pass through?

Answer 10

• lesser petrosal nerve (foramen ovale)
• sympathetic plexus from internal cartoid plexus (around intenral carotid artery) (carotid canal)
• branch of glossopharangeal nerve (tympanic branch)

Question 11

Chorda tympanie - where form , where does it go? with which nerve?

Answer 11

from facial nerve, runs through middle ear, -chroda tympani branch - goes through posterior wall of middle ear and then goes tongue with lingual nerve to give taste

Question 12

Anterior wall - carotid wall - waht is improtant to avoid during surgeyr?
-what makes up this wall?

Answer 12

• important if operating on midle ear nto to push to hard on anterior membrane as thsi sits next to the internal carotid artery
• pharyngotympanic tube
• tensor tympanic muscle
• corda tympani nerve
• sympathetic plexus that goes thru the middle ear

Question 13

posterior wall

Answer 13

corda tympani runs here
pyramidal eminence
-entry to mastoid antrum

Question 14

What runs through middle ear

, innovation

Answer 14

Muscles
Ossicles (stapes, malleus, incus)
Corda tympani nerve Tympanic nerve plexus

Innovation - tympanic pleux, and amstoid antrum
, numebr 9
-facial nerve,

Blood supply - brancehs of exernal carotid - external aucostic meatus, and middle ear