Lecture 28: Ear

Question 1

What is the order of structures in the middle ear from most external to internal

Answer 1

Tympanic membrane—> auditory ossicles (malleus, incus, stapes)—> oval window

Question 2

What are some functions of the ear

Answer 2

Balance, orientation and hearing

Question 3

Balance and orientation

Answer 3

Detection of movement of the body relative to the outside world

Question 4

Hearing

Answer 4

Detection of movement of the outside world

Question 5

What are the three parts of the hearing and balance apparatus

Answer 5

Inner ear, middle ear, and external ear

Question 6

What is the inner ear composed of and what is the function

Answer 6

Fluid filled space within the petrous portion of the temporal bone

Fx: hearing and balance

Question 7

What is the middle ear composed of and what is the function

Answer 7

Air filled space within the petrous and tympanic portions of the temporal bone

Fx: hearing

Question 8

Where does the external ear emerge from and what is it continued by

What is the function

Answer 8

Emerges from the tympanic part of the temporal bone and is continued by additional cartilaginous pieces

Fx: hearing

Question 9

Sound waves that pass through water (ex: body of fish) don’t ___ when transferred to fluids of inner ear and therefore only require ____

Answer 9

Lose energy and therefore only require internal ear structures

Question 10

Sound waves traveling through the air reflex off a surface much denser and the waves ____ in transfer from air to ear fluids and therefore require ___

Answer 10

Lose energy and therefore require hearing structures to amplify the weak waves

Question 11

What structure amplifies the weak waves

Answer 11

Tympanic ear

Question 12

What is the tympanic ear

Answer 12

Ear drum, air filled middle ear and bony connection to inner ear

Question 13

What is the primary function of the middle ear or tympanic cavity

Answer 13

Transmit sound vibration from the lateral external ear to the more medial inner ear

Question 14

What bone transmits vibrations from outside the head to the inner ear

Answer 14

Stapes

Question 15

What bone has an oval-shaped footplate that fits into the oval window and causes the vibrations in the perilymph of the inner ear

Answer 15

Stapes

Question 16

What is the incus

Answer 16

Intermediate bone between the two other bones of the ossicular chain

Question 17

What type of joint connects the incus to stapes and incus to malleus

Answer 17

Synovial joint

Question 18

What is the malleus

Answer 18

Body of the malleus is fixed to the tympanic membrane so that the vibrations of the membrane are passed along the ossicular chain

Question 19

What are the two skeletal muscles within the middle ear that are associated with the ossicles

Answer 19

Tensor tympani and stapedius

Question 20

Where does the tensor tympani originate and insert

Answer 20

Comes from the anterior wall of the middle ear and inserts onto the body of the malleus

Question 21

What nerve innervates the tensor tympani

Answer 21

Mandibular nerve CN V3

Question 22

Where does the stapedius originate and insert

Answer 22

Comes from the posterior wall of the middle ear and inserts onto the head of the stapes

Question 23

What nerve innervates the stapedius

Answer 23

Facial nerve- CN VII

Question 24

What is the function of the tensor tympani and the stapedius

Answer 24

Act to clarify hearing and protect from excessively loud noises

Question 25

What nerve does the mucosa lining in the middle ear, including the inner surface of the tympanic membrane send its sensory input on

Answer 25

Glossopharyngeal nerve

Question 26

What nerve carries preganglionic parasympathetics from the glossopharyngeal nerve through the middle ear cavity to the otic ganglion

Answer 26

Minor petrosal nerve

Question 27

What nerve travels through the internal acoustic meatus to the sytlomastoid foramen and runs through the posterior wall of the tympanic cavity

Answer 27

Facial nerve CN VII

Question 28

What are the two branches off the facial nerve that run through or in the wall of the cavity

Answer 28

Major petrosal nerve and chorda tympani

Question 29

What nerve carries preganglionic parasympathetic axons from CN VII to the pterygopalatine ganglion

Answer 29

Major petrosal nerve

Question 30

What branch of CN VII carries both preganglionic sympathetic input to the Mandibular and sublingual ganglia and taste from the rostral portion of the tongue

Answer 30

Chorda tympani

Question 31

What nerve crosses the tympanic membrane to get on the lingual nerve in the infratemporal fosssa and then its axons hitchhike to the oral cavity on the lingual

Answer 31

Chorda tympani

Question 32

For most efficient function of tympanic membrane what must the air pressure in the middle ear be in relation to the outside pressure

Answer 32

The air pressure in the middle ear cavity must match the outside pressure

Question 33

What connects the middle ear to the nasopharynx

Answer 33

Auditory tube

Question 34

How does the auditory tube maintain pressure

Answer 34

Tube is typically pressed closed and must be activity opened to equalize air pressure

Question 35

What two muscles are involved in opening the auditory tube

Answer 35

Tensor veli palatine and levator veli palatine

Question 36

Otitis media

Answer 36

Infection of the middle ear cavity/build up of infectious fluid in the tympanic cavity

Question 37

How can otitis media damage hearing

Answer 37

Negatively impact the sensitivity of hearing by dampening the vibrations of the tympanic membrane as well as possibly lesion it any nerves that pass through

Question 38

What structure might be sensitive upon palpation in animals with otitis media

Answer 38

Tympanic bulla

Question 39

How can infections of the tympanic bulla/otitis media be drained

Answer 39

Surgically open the tympanic bulla rostromedially into the nasopharynx

Question 40

What is the function of the auricle (pinna)

Answer 40

Serves to funnel and focus sound into the external auditory canal Highly mobile auricles help with detection of directionality of sound

Question 41

Describe the anatomical position of erect, alert auricles

Answer 41

Concave, lightly haired surface is rostral Convex, furred surface is caudal

Question 42

What are some additional functions of the ear beyond hearing, balance, and orientation

Answer 42

Thermoregulation, communication and improved olfactory efficiency

Question 43

What two canals lead from the auricle to the tympanic membrane

Answer 43

Vertical canal—> horizontal canal

Question 44

What is the ceruminous gland

Answer 44

Earwax gland that helps keep the casual clean and free of particles that might interfere with the sensitivity of the tympanic membrane

Question 45

What is the suctiform cartilage

Answer 45

Smaller isolated cartilage, associated with the musculature of the external ear

Question 46

What is the function of the extensive auricle musculature

Answer 46

Provide fine control of the position and attitude of the auricle, important in facial expression

Question 47

What artery branches off the superficial temporal artery and supplies some of the rostral concave surface of the external ear

Answer 47

Rostral auricular

Question 48

What artery branches off the external carotid artery and has four large branches-medial, lateral, intermediate, and deep that supply the auricle cartilage and rostral surface of external ear

Answer 48

Caudal articular artery

Question 49

What happens to the skin and cartilage of the ear when an aural hematoma forms

Answer 49

Blood pools and separates the skin from the underlying cartilage

Question 50

What carries sensory innervation from the caudal surface of the auricle

Answer 50

Ventral and dorsal rami of C2

Question 51

What nerve comes off the ventral rami of C2 to provide sensory innervation to the lateral side of the caudal external ear

Answer 51

Great auricular nerve

Question 52

What nerve comes off of the dorsal rami of C2 to supply the medial side of the caudal external ear

Answer 52

Great (major) occipital nerve

Question 53

What nerve carries sensory innervation on the rostral, medial part of the external ear

Answer 53

Auriculotemporal nerve- division of CN V3

Question 54

What nerve provides sensory innervation to the petrous portion of the temporal bone

Answer 54

Vagus CN X