GA: Ear

Question 1

What are the 3 general divisions of the ear?

Answer 1

Inner ear: auricle (pinna) + external acoustic meatus (ear canal)

Middle ear: Tympanic cavity + epitympanic recess (ossicles: malleus, incus, stapes + chorda tympani N. + tympanic plexus)

Internal Ear: Vestibulocochlear organ (hearing _ balance)

Question 2

Parts of Auricle

Answer 2

Question 3

What is the blood supply for the auricle (& pinna)?

Answer 3

Posterior Auricular + Superficial Temporal A.’s

(from ECA)

Question 4

What is the innervation for the auricle?

Answer 4

Great auricular N.

Auriculotemporal N.

Vagus N.

Facial N.

Question 5

What causes an auricular hematoma?

Answer 5

Trauma to ear –> causes blood to build up between perichondrium + cartilage

If not drained, fibrous tissue can form and this can cause califlower ear

Question 6

What does the external acoustic meatus consist of?

Answer 6

lateral 1/3 = cartilage

medical 1/3 = bone

Question 7

Which way do you pull an ear during an exam?

Answer 7

Posterior, Superior, and slightly lateral

Question 8

What is otitis externa?

Answer 8

“swimmers ear”

Infection of external acoustic meatus

Risk factors: excessive moisture (pool), trauma (cleaning), anything the covers ear canal (earphones)

Question 9

What is the purpose of the tympanic membrane?

Answer 9

It separates the external acoustic meatus from the middle ear.

Reflects cone of light

Question 10

Where are the incus + malleus heads found?

Answer 10

In the epitympanic recess of

Question 11

Which “portion” is the cone of light in?

Answer 11

Anterior and Inferior

Question 12

What is otitis media?

Answer 12

Infection of the middle ear

Causes swelling of tympanic membrane and can block pharyngotympanic tube (eustacian tube)

Question 13

Describe the steps taken in treatment of chronic middle ear infections (i.e. myringotomy and tympanostomy).

Answer 13

You would place a tympanostomy tube.

myringotomy –> incision to open eardrum

tympanostomy –> tube placed for continual drainage

Question 14

What is the middle ear cavity roof boundry?

Answer 14

Tegmen tympani bone

Separates tympanic cavity from middle cranial fossa (temporal bone & brain)

Infection here can cause meningtitis

Question 15

What is the middle ear cavity floor boundry?

Answer 15

bone

Separates tympanic cavity from the bulb of the internal jugular V.

Question 16

What is the middle ear lateral boundry?

Answer 16

Tympanic membrane

Separates tympanic membrane from external ear

Question 17

What is the middle ear medial boundry?

Answer 17

Promontory (formed by cochlea), oval window, round window, and prominence of facial canal

Separates the tympanic cavity from the inner ear

Question 18

What is the middle ear posterior boundry?

Answer 18

Aditus to mastoid antrum, canal for facial nerve

Separates tympanic cavity from mastoid air cells + facial canal

Question 19

What is the anterior wall middle ear boundry?

Answer 19

Opening of pharyngotympanic tube + canal for tensor tympani

Separates tympanic cavity from Carotid

*If infection errodes through anterior wall you can hit carotid*

Question 20

What are the components of the middle ear?

Answer 20

Ossicles (malleus (tip = umbo), incus, stapes) MIS

Stapedius + tenso tympani M.’s

Chorda tympani N.

Tympanic plexus

Question 21

What is the function + innervation of the tensor tympani muscles in the middle ear?

Answer 21

Help dampen loud sounds.

It inserts on mallelus and pulls it medially, and tenses the tympanic membrane so vibrations can’t move as well. This action prevents hearing damage from loud sounds.

Innervated by CN V3

Question 22

What is the function + innervation of the stapedius M.?

Answer 22

Inserts on stapes

Prevents damage from loud sounds

CN VII

Question 23

The facial nerve gives off ________ and carries parasympathetic fibers to preform __________.

Answer 23

Chorda tympani

Taste on anterior 2/3 of tongue

Question 24

The glossopharyngeal N. gives off _______ which gives rise to the parasympathetic ________ N.

Answer 24

Tympanic plexus

Lesser petrosal N. –> innervates parotid

Question 25

What CN forms greater petrosal N. + what does it supply?

Answer 25

7

eye

Question 26

What cranial N. forms lesser petrosal and what does it supply?

Answer 26

9

parotid gland

Question 27

What is the course of the facial N. through the temporal bone?

Answer 27

*carries pre-ganglionic parasympathetic fibers to submanidbular + sublingual glands*

Facial N. –> Chorda tympani –> Lingual N. –> Submandibular Ganglion –> sublingual + submandibular glands

Question 28

In the inner ear what are the two major stuctures + their components?

Answer 28

1. Bony Labyrinth: fluid filled cavities in the petrous part of the temporal bone
   - Cochlea + Vestibule + Semicircular canals
2. Membranous Labyrinth: Communicating sacs that are suspended in the bony labyrinth
   - Vastibular labyrinth (utricle + saccule), semicircular ducts, cochlear labyrinth

Question 29

What are the semicircular canals of the bony labyrinth filled with?

Answer 29

Perilymph

Question 30

______ N. innervates the membranous labyrinth and they are filled with _______.

Answer 30

CN 8

endolymph

Question 31

Question 32

What disorder of the inner ear causes severe dizziness (vertigo), ringing in the ears (tinnitus), hearing loss, and a feeling of fullness or congestion in the ear?

Answer 32

Meniere’s Disease