1 - Zill - Ear

Question 1

Middle Ear

Amplification?

Dampening?

Answer 1

1. Bones link tympanic membrane to cochlear, amplify force/area
2. Muscles can dampen sound (Clinical: Bell’s Palsy and loud own-voice)

Question 2

Areas of Sound Conduction and Detection

Sensorineural?

Answer 2

Outer and Middle Ear = Conduction

Inner Ear = Detection, Sensorineural

Question 3

Clinical: Weber Test

Answer 3

Function test for inner ear (bone vibrations) or Sensorineural hearing loss

Tuning fork is placed on calvarium, vibrations conducted to cochlea and perceived as sound by patient

Question 4

Conductive vs Sensorineural Hearing Loss

Answer 4

Conductive: Damage to outer or middle ear (tympanic membrane, auditory ossicles, bones)

Sensorineural: Damage to inner ear (cochlea)

Question 5

Clinical: Sensory Innervation of Outer Ear

Symptoms?

Answer 5

Cranial Nerves: V, VII, IX, X (5, 7, 9, 10)

Patients with Bell’s Palsy can suffer earache

Question 6

Clinical: External Auditory Meatus - Child Development

Answer 6

Ext. Auditory Meatus is straight in children, and curved anteriorly in adults

Question 7

Boundaries of Middle Ear

Roof?

Floor?

Ant. Wall?

Post. Wall?

Lat. Wall?

Med. Wall?

Answer 7

**Roof: Tegmen Tympani - Thin plate of temporal bone, can be eroded by infections**

**Floor: Jugular Foramen - Internal Jugular can rupture below**

Ant. Wall: Opening of Auditory Tube

Post. Wall: Mastoid Air Cells, Cranial Nerve VII

Lat. Wall: Tympanic Membrane (“Ear Drum”)

Med. Wall: Oval Window = attach stapes, Round window

Question 8

Auditory Tube - Composition

Answer 8

Ant. 2/3 = Cartilage

Post. 1/3 = Bone

Question 9

Otitis Media

Clinical Pathology?

Treatment?

Cause?

Answer 9

Middle Ear Infection, common in children; Middle Ear is Dead End Cavity

- - -

Respiratory Infection an spread to Auditory Ossicles and result in Hearing loss; Prolonged infection can erode Tegmen Tympani to Brain

- - -

Treatment is Tympanostomy - “tubes” through tympanic membrane

Orientation of Aud. Tube changes from Horizontal to Angled with cranial growth; diameter also increases

Question 10

Auditory Ossicles

Answer 10

1. Malleus
2. Incus
3. Stapes

Link tympanic membrane to oval window and cochea;

Arrangement acts as lever to increase force

Question 11

What nerve is courses the surface of the Tympanic Membrane, and what is it a branch of?

Answer 11

Chorda Tympani

Branch of Cranial Nerve VII

Question 12

Muscles of Middle Ear

Tensor Tympani

Action?

Innervation?

Answer 12

Action: Tenses tympanic membrane to dampen sound

Innervation: V3

Question 13

Muscles of Middle Ear:

Stapedius

Action?

Innervation?

Answer 13

Stapedius

Action: Dampens sound

Innervation: Cranial Nerve VII

Question 14

Hyperacousia

Answer 14

Damage to Cranial Nerve VII

Sounds seem too loud; including own voice;

Stapedius paralyzed

Symptom of Bell’s Palsy

Question 15

Clinical: Sensory Innervation of Middle Ear

Result w/Ear Infection?

Answer 15

Visceral Sensory

Cranial Nerve IX (Glossopharyngeal)

- - -

Can’t localize pain, “My Head Hurts” with middle ear infections

Question 16

Tympanic Nerve

Answer 16

Forms tympanic plexus, visceral sensory to middle ear, Mastoid sinus, Auditory Tube

Branch of CN IX (Glossopharyngeal)

Question 17

Branches of CN VII (Facial) in Ear

Answer 17

CN VII enters Interal Auditory Meatus on path to Facial Canal

Branches:

Greater Petrosal N. - Visceral Motor - parasympathetics to lacrimal gland, muscous gland of nose and palat (visceral sensory to nasopharynx)

Stapedial N. - Branchiomotor to Stapedius (Hyperacousia)

Chorda Tympani -

A) Taste to Ant 2/3 Tongue

B) Parasympathetics to Submandibular, Sublingual, Salivary Glands

Question 18

Chorda Tympani (odd targets)

Clinical Relevance?

Answer 18

1. Taste to Ant. 2/3 Tongue

2. Parasympathetics to Submandibular, Sublingual, Salivary Glands
   * No real function in middle ear, only result of evolution*
   - - -

Clinical: If eardrum is pierced, you can lose taste