Lecture 16: Anatomy and Histology of the Ear

Question 1

What composes the external ear?

Answer 1

Auricle to Tympanic Membrane

Question 2

What composes the middle ear?

Answer 2

Tympanic Membrane to Oval Window

Question 3

What composes the inner ear?

Answer 3

Oval Window to Internal Acoustic Meatus

Question 4

What type of cartilage is the external ear mostly made up of?

Answer 4

Elastic Cartilage

Question 5

What supplies the external ear?

Answer 5

Posterior Auricular Artery (from ECA)

Superficial Temporal Artery (from ECA)

Question 6

What provides sensory innervation to the external ear?

Answer 6

1. Facial Nerve
2. Cervical Plexus: Lesser Occipital and Greater Auricular Nerves
3. Auriculotemporal Nerve (V3)
4. Vagus/Glossopharyngeal Nerve

Question 7

What innervates the superior part/roof of the external acoustic meatus?

Answer 7

Facial Nerve

Question 8

What innervates the posterior part of the external acoustic meatus?

Answer 8

Greater Auricular Nerve (Cervical Plexus)

Question 9

What innervates the anterior part of the external acoustic meatus?

Answer 9

Auriculotemporal Nerve (V3)

Question 10

What innervates the inferior part/floor of the external acoustic meatus?

Answer 10

Vagus: Arnold Nerve

-plays a role in the cough reflex

Question 11

What glands make ear wax?

Answer 11

Ceruminous Glands

Question 12

What is the composition of the external acoustic meatus?

Answer 12

Outer ⅔: Soft CT and Cartilage (similar to external ear)
-where you can see ceruminous and sebaceous glands + hair follicles
Inner ⅓: Just skin and bone

Question 13

Where is the cone of light?

Answer 13

Anterior, inferior quadrant of Tympanic Membrane

Question 14

What makes up the roof of the middle ear?

Answer 14

Tegmental Wall (from Temporal Bone)
-Separates ear from brain/middle cranial fossa

Question 15

What makes up the floor of the middle ear?

Answer 15

Jugular Wall

-Separates ear from bulb of Internal Jugular Vein

Question 16

What makes up the lateral wall of the middle ear?

Answer 16

Membranous Wall (going to external ear)

Question 17

What makes up the medial wall of the middle ear?

What is found at this wall?

Answer 17

Labyrinthine Wall (Oval and Round Windows)

• Lateral Semicircular Canal
• Facial Canal and Nerve
• Promontory of Labyrinthine Wall

Question 18

What makes up the posterior wall of the middle ear?

Answer 18

Mastoid Wall

-Separates tympanic cavity from mastoid air cells and facial canal

Question 19

What can be found at the anterior wall of the middle ear?

Answer 19

Pharyngotympanic Tube
Tensor Tympanic Muscle
-Separates Tympanic Cavity from Internal Carotid Artery

Question 20

What does the pharyngotympanic tube connect?

Answer 20

Middle ear to nasopharynx

Question 21

What does the pharyngotympanic tube do?

Answer 21

Equalize pressure

Question 22

What two muscles expand the pharyngotympanic tube?

Answer 22

Levator Veli Palatini Muscle

Tensor Veli Palatini Muscle

Question 23

What type of epithelium is found on the pharyngotympanic tube?

Answer 23

Pseudo-stratified Epithelium

Question 24

What three bones make up the auditory ossicles in the middle ear?
What pharyngeal arches are they from?

Answer 24

Malleus (PA 1)
Incus (PA 1)
Stapes (PA 2)

Question 25

What does the auditory ossicles do?

Answer 25

Transmit sound from the air to the fluid filled concha

Question 26

What does the Tensor Tympani Muscle do? | What nerve innervates it?

Answer 26

Dampens loud sounds by pulling on handle of malleus | Innervated by CN V3

Question 27

What does the Stapedius Muscle do? | What nerve innervates it?

Answer 27

Dampens vibrations and limits excess movement of stapes bone (at the neck) Innervated by CN VII

Question 28

Where is the bony labyrinth located?

Answer 28

Petrous Region of Temporal Bone

Question 29

What separates bony labyrinth with membranous labyrinth?

Answer 29

Perilymph

Question 30

What lymph is found in membranous labyrinth?

Answer 30

Endolymph

Question 31

What sections are found in the membranous labyrinth? | What do they do?

Answer 31

Semicircular Canals: Equilibrium Utricle and Saccule: Acceleration Cochlear Duct: Hearing Sensory Cells

Question 32

What is kinocilium?

Answer 32

Specialized hair cells that can be displaced and result in depolarization or hyper polarization of the hair cells

Question 33

What are the three sections of the Cochlear Duct? | What lymph does each section contain?

Answer 33

1. Scala Vestibule - Perilymph 2. Scala Media - Endolymph 3. Scala Tympani - Perilymph

Question 34

What makes up the roof and floor Scala Media?

Answer 34

Roof: Vestibular Membrane Floor: Basilar Membrane

Question 35

What is found in the Basilar membrane?

Answer 35

Organ of Corti

Question 36

What is Organ of Corti composed of?

Answer 36

Hair cells (sensory) Support Cells Pillar Cells

Question 37

What is the ratio of outer hair cells to inner hair cells?

Answer 37

3:1

Question 38

Where is stereocilia found?

Answer 38

Overlying tectorial membrane, which is extending from spiral lamina

Question 39

What is the function of the external ear?

Answer 39

Directs sound waves to external auditory meatus

Question 40

What is the function of the middle ear?

Answer 40

1. Takes sound waves and turns them into physical energy that pushes against auditory ossicles and then pushes on the oval window 2. Controls pressure in the middle ear via Pharyngotympanic Tube

Question 41

What is the function of the inner ear?

Answer 41

1. Transform sound waves to the brain | 2. Balance

Question 42

How does sound move in the inner ear?

Answer 42

1. Stapes moves oval window, causing the perilymph to change pressure in Scala Vestibule. 2. This disturbs endolymph in scala media and displaces basilar membrane. 3. Stereocilia in hair cells is distorted. Organ of Corti cells are distorted and initiates a signal via CN VIII. 4. Perilymph in Scala Tympani takes the pressure and it exits via round window.

Question 43

What are the three canals in the semicircular canals and what is their axis?

Answer 43

Anterior: Sagittal Plane Lateral: Transverse Plane Posterior: Coronal Plane

Question 44

What is displaced by fluid motion within semicircular canal?

Answer 44

Cupulla: has hair cells with stereocilia

Question 45

What covers hair cells in the vestibule?

Answer 45

Otolithic Membrane

Question 46

What does the utricle sense?

Answer 46

Horizontal Acceleration

Question 47

What does the saccule sense?

Answer 47

Vertical Acceleration

Question 48

Where is perilymph drained to?

Answer 48

Subarachnoid Space

Question 49

Where is endolymph drained to?

Answer 49

Venous Sinuses of Dura Mater

Question 50

How does elastic cartilage get its nutrients?

Answer 50

Periochondrium

Question 51

What pathologies are associated with external ear?

Answer 51

Cauliflower Ear | Wrestling

Question 52

What is mastoiditis?

Answer 52

Infection of mastoid cells that can spread into cranial fossa

Question 53

How can the tympanic membrane be damaged?

Answer 53

1. Medial Ear pressure from fluid | 2. External Trauma

Question 54

What is Otitis Media?

Answer 54

Infection of the middle ear (can be viral, bacterial, fungal, etc). The ear is filled with fluid or pus. Tympanic membrane is red and bulged

Question 55

What is Ménière's Syndrome?

Answer 55

Increased endolymph that leads to abnormal signaling. | Can cause dizziness, vertigo, and possible hearing loss

Question 56

What can cause conductive hearing loss?

Answer 56

Problems with outer or middle ear

Question 57

What can cause sensorineural hearing loss?

Answer 57

Damage to inner ear or auditory nerve

Question 58

What can cause central hearing loss?

Answer 58

Problems in CNS

Question 59

Why do young children suffer from otitis media more than adults?

Answer 59

Pharyngotympanic tube is at a more shallow angle, allowing for less drainage and pressure equalization of the inner ear