10. Ear Anatomy and Histology (Fellow)

Question 1

What nerves innervate the tympanic membrane?

Answer 1

External surface: Auriculotemporal nerve and Auricular branch of the vagus.

Internal surface: Glossopharyngeal (CN IX)

Question 2

What would be affected in an erosion through the medial wall of the middle ear?

Answer 2

The inner ear, the oval and round windows, the promontory of the labyrinthine wall, and the nerve plexus thereof (tympanic and lesser petrosal nerves).

Question 3

Greater and lesser petrosal nerves carry what type of nerve fibers?

Answer 3

Parasympathetic (general visceral efferent) fibers.

Question 4

What cranial nerve does the tympanic nerve come off of?

Answer 4

The glossopharyngeal (CN IX)

Question 5

Which portion of the tympanic membrane is more vascular?

Answer 5

The superior portion.

Question 6

What is a myringotomy, and where is it performed?

Answer 6

Myringotomy: lesion to open up the eardrum. Made in the posterior inferior quadrant to avoid vasculature.

Question 7

The tympanic plexus primarily contains fibers from which cranial nerve?

Answer 7

Glossopharyngeal, via the tympanic branch.

Question 8

Answer 8

Question 9

What is the blood supply to the auricle of the ear?

Answer 9

Posterior auricular A and superficial temporal A.

Question 10

What would be affected in an erosion through the posterior wall of the middle ear?

Answer 10

Mastoid antrum (containing mastoid air cells) and facial canal (containing facial nerve).

Question 11

Where are the heads of the incus and malleus found?

Answer 11

In the epitympanic recess.

Question 12

What would be affected in an erosion through the anterior wall of the middle ear?

Answer 12

Internal carotid artery, opening for the pharyngotympanic tube, and the canal for the tensor tympani.

Question 13

What would be affected in an erosion through the lateral wall of the middle ear?

Answer 13

Tympanic membrane and external ear.

Question 14

What are the respective functions of the greater and lesser petrosal nerves?

Answer 14

Greater petrosal: parasympathetics to the eye from facial N.

Lesser petrosal: parasympathetics to the parotid gland from glossopharyngeal N.

Question 15

Answer 15

Question 16

List the nerves that innervate the represented parts of the auricle of the ear.

TM Innervation:

Answer 16

(add to image: Auricular branch of Vagus and glossopharyngeal)

Superior: VII

Anterior: V

Posterior: X (arnold, cough) and C3

Question 17

What would be affected in an erosion through the roof of the middle ear?

Answer 17

The tegmen tympani (bone) and the dura of the middle cranial fossa.

Question 18

What is the bony labyrinth filled with?

What is the membranous labyrinth filled with?

Answer 18

Bony labyrinth: perilymph.

Membranous labyrinth: endolymph.

Question 19

What nerve gives rise to the greater petrosal nerve?

Answer 19

Facial nerve.

Question 20

What would be affected in an erosion through the floor of the middle ear?

Answer 20

Bulb of the internal jugular vein.

Question 21

Which of these spaces contain endolymph, and which contain perilymph?

Answer 21

The scala vestibuli and the scala tympani are filled with perilymph. The cochlear duct is filled with endolymph.

Question 22

What nerve gives rise to the lesser petrosal nerve?

Answer 22

The tympanic nerve - a branch of the glossopharyngeal nerve.

Question 23

Answer 23

Question 24

Answer 24

Note that “malleolus” is actually “malleus.” This slide has a typo.

Question 25

Which is more anterior, the cochlea or the vestibular apparatus?

Answer 25

The cochlea.

Question 26

Ear Anatomy

EAM:

PT:

Answer 26

distal 2/3 cartilage, proximal 1/3 bone

distal 2/3 bone, proximal 1/3 cartilage

Question 27

Functions and Muscles of the Pharyngotympanic Tube

Answer 27

Functions: pops the ear

Levator Veli Palatini contracts longitudinally to PUSH against one wall

Tensor Veli Palatini PULLs on the other wall

Question 28

Ossicle Anatomy

Malleus:

Incus:

Stapes:

Answer 28

head, neck, handle

body, short and long processes (short connected to posterior wall)

base vibrates on the oval window

Question 29

Muscles of the Inner Ear

Tensor Tympani

Stapedius

Answer 29

on PT, greater wing of sphenoid, petrous part of temporal bone to handle of malleus

CN V

on pyramidal eminence on posterior wall of tympanic cavity to foramen on stapes

CN VII

BOTH limit volumn/dampen sound (reduce amplitude, prevent excessive movement)

Question 30

Know What and Where Stria Vascualris is

Answer 30

Question 31

Know the Organ of Corti

Answer 31

Question 32

Understand depolarization and hyperpolarization of hair cells

Answer 32

otoliths bend hair cells

if they are bent toward the kinocillium then that is a depolarization (opens K channels)

if they are bent away from the kinocillium, that is a hyperpolarization (closes K channels)

Otoliths do this in the utricle and saccule, and gel does this in the semicircular canals

these can be targeted by certain drugs/abx and cause hearing issues

Question 34

Composition, location, and origination of Perilymph

Answer 34

similar to CSF

drains via perilymphatic duct into SA space

from perisosteum, located between bony and membranous labyrinth (in the bony part)

Question 35

Composition, location and origination of endolymph

Answer 35

high H, low Na

from stria vascularis

drains via endolymphatic duct into venous sinuses of dura

found in membranous labyrinth

Question 36

Brief Notes on Ear Pathology

Answer 36

damaged TM (pressure, fluid or trauma, usually heal, may need antibiotics)

Mastoiditis (infected mastoic cells can spead into cranial fossa, tx ABX)

Otitis Media (fluid in middle ear, TM red and bulging, #1 reason for hospital visits)

Meniere’s Syndrome (vertigo and tinnitus, hearing loss, increased endolymph, tx with meds or surgery)

Viral Labyrinthitis (similar to Meniere’s but usually self limiting, resolved in 1wk)