Ear

Question 1

Describe middle ear

Answer 1

Tympanic cavity
Small hour-glass shaped cavity embedded in petrous temporal bone
Has ossicles

Question 2

Describe the internal/inner ear

Answer 2

Series of interconnected fluid-filled (endolymph) ducts, tubes, sacs (membranous labyrinth) suspended within fluid-filled (perilymph) bony canals and cavities (osseous labyrinth)

Question 3

Match air transmission, bone conduction, and fluid conduction to the parts of the ear

Answer 3

Air transmission: external auditory meatus
Bone conduction: ossicles of middle ear
Fluid conduction: inner ear

Question 4

Describe the parts of the auricle/pinna

Answer 4

Helix: outer free margin
Lobule
Tragus and antitragus: protect external auditory meatus
Concha: central depression

Question 5

What innervates the pinna?

Answer 5

GSA sensory fibers from auriculotemporal (V3), lesser occipital (C2-3), great auricular (C2-3)

Question 6

What innervates the skin of the concha?

Answer 6

VII, IX, X

Question 7

What is the blood supply to the auricle?

Answer 7

Superficial temporal and posterior auricular arteries

Question 8

Describe auricular hematoma

Answer 8

Trauma to pinna may cause hemorrhaging in subcutaneous tissue
If hematoma is not evacuated and bandaged, subsequent scar tissue may grossly deform the auricle (cauliflower ear)

Question 9

What does the skin lining the outer 1/3 of the external auditory meatus contain? Clinical relevance?

Answer 9

Sebaceous and seruminous glands, which secrete cerumen (ear wax)
Accumulation of cerumen may be firmly adherent to epithelia of EAM and/or tympanic membrane
Causal removal of a mass of ear wax may avulse the tympanic membrane and ossicle
When infected, the furuncle is very painful due to close adhereance of skin to underlying periosteum

Question 10

What innervates the outer epidermis or skin of the tympanic membrane?

Answer 10

GSA fibers from trigeminal and vagus nerves

Question 11

Describe the pars tensa

Answer 11

Middle fibrous layer of the most of the tympanic membrane

Attached to fibrocartilaginous ring which rests in tympanic sulcus and manubrium of malleus

Question 12

Describe the pars flaccida

Answer 12

Part in the antero-superior quadrant of the tympanic membrane that does not have the fibrous layer

Question 13

What innervates the inner mucous membrane of the tympanic membrane?

Answer 13

GVA fibers of glossopharyngeal nerve via tympanic plexus

Question 14

What is the central concavity of the tympanic membrane?

Answer 14

Umbo

Question 15

What do the borders of the pars flaccida form? What courses through them?

Answer 15

Anterior and posterior mallear folds

Chora tympani n

Question 16

What middle ear structures are in the superio-posterior area of the tympanic membrane?

Answer 16

Long process of incus
Stapes
Fenestra vestibuli

Question 17

What middle ear structures are in the superio-anterior area of the tympanic membrane?

Answer 17

Auditory tube

Question 18

What middle ear structures are in the inferio-posterior area of the tympanic membrane?

Answer 18

Fenestra cochleae

Question 19

What middle ear structures are in the inferio-anterior area of the tympanic membrane?

Answer 19

Carotid canal

Question 20

Describe otitis media

Answer 20

Inflammation of middle ear cavity that is relatively common in infants and children
May result in accumulation of fluid & mucous and decrease in hearing
More common in infants because auditory tubes are oriented horizontally which impedes drainage from tympanic cavity
Tubes are downward in adults

Question 21

Describe fractures of the petrous temporal bone

Answer 21

Severe head trauma may cause basilar skull fractures such as transverse or longitudinal fractures of temporal bone
Otorrhea, otorrhagia, vestibular disturbances, deafness, or Bell’s palsy may result
Often associated with brain trauma and considerable mortality/morbidity

Question 22

What structures are near the medial wall of the middle ear cavity?

Answer 22

Semicanal for facial nerve
Fenestra vestibuli 
Stapes
Stapedius
Pyramid
Prominence
Tympanic plexus
Tensor tympani
Fenestra chocleae
Auditory tube

Question 23

What structures are near the lateral wall of the middle ear cavity?

Answer 23

Epitympanic recess
Malleus
Incus
Tympani membrane
Chorda tympani
Auditory tube
Tensor tympani m
Facial n

Question 24

Describe the course of the facial nerve in the ear

Answer 24

Facial nerve is NOT in middle ear
After leaving brainstem, facial nerve travels laterally in internal auditory meatus before entering facial canal
Within the canal, geniculate ganglion is located just above and medial to promontory of middle ear cavity
At the level of the ganglion, the nerve turns sharply and posteriorly as it forms external genu
After about 1.0 cm, the nerve courses downward, sends a branch to stapedius muscle, and exits stylomastoid foramen

Question 25

Where is the cochlea in relation to the facial nerve?

Answer 25

Cochlea is anterior

Question 26

What does the external ear include?

Answer 26

Auricle (pinna) | External auditory meatus

Question 27

What forms the roof of the tympanic cavity?

Answer 27

Tegmen tympani

Question 28

What forms the floor of the tympanic cavity?

Answer 28

Superior bulb of the internal jugular vein

Question 29

Describe the articulations of the malleus and relationship to chorda tympani n

Answer 29

Manubrium of malleus is attached to fibrous layer of tympanic membrane The head articulates with incus in epitympanic space Chorda tympani n crosses the neck of the malleus

Question 30

Describe the articulations of the incus

Answer 30

Incus is wedged between malleus and stapes Body articulates with malleus at incudo-mallear joint Its long crus articulates with head of stapes

Question 31

Describe the articulations of the stapes

Answer 31

Head articulates with long crus of incus Anterior and posterior crura connect head to footplate Footplate articulates with fenestra vestibuli

Question 32

Describe otosclerosis

Answer 32

Ossification or scarring of small ossicular joints that prevents transmission of sound from tympanic membrane to fenestra vestibuli May result in significant hearing impairment Typically, tests for bone conduction are normal, but nerve conduction is reduced

Question 33

Describe location of tensor tympani muscle

Answer 33

Located in semicanal above auditory tube, from which it arises Its tendon loops laterally around processus cochleariformis and inserts on handle of malleus

Question 34

What innervates tensor tympani muscle?

Answer 34

Branch of mandibular nerve (V)

Question 35

What is the function of the tensor tympani muslce?

Answer 35

Tightens tympanic membrane and attenuates its vibrations

Question 36

Describe location of stapedius muscle

Answer 36

Located in pyramid on posterior wall of middle ear cavity | Its tendon exits a minute opening at apex of pyramid and inserts on neck of stapes

Question 37

What innervates the stapedius muscle?

Answer 37

Facial nerve

Question 38

What is the action of the stapedius muscle?

Answer 38

Pulls stapes out of fenestra vestibuli | This is a protective mechanism to prevent excessive movement of stapes due to loud sound

Question 39

What is the blood supply to the middle ear cavity?

Answer 39

Stylomastoid branch of posterior auricular artery | Anterior tympanic artery

Question 40

What are the functions of the inner ear?

Answer 40

Cochlear receptors for hearing Receptors in semicircular ducts: detect angular acceleration Receptors in sacculus and utricle: detect linear acceleration

Question 41

What does the cochlear division of VIII nerve innervate?

Answer 41

Organ of Corti (spiral organ) | Conveys auditory information

Question 42

What does the vestibular division of VIII nerve innervate?

Answer 42

Maculae utricle, saccule, and cristae ampullaris of semicircular ducts Conveys static and dynamic position-sense information for equilibrium

Question 43

What is the blood supply to the inner ear? Clinical relevance?

Answer 43

Labyrinthine artery, which a branch of the anterior inferior cerebellar artery Arteriosclerosis of this artery may result in vertigo, nausea, and other inner ear abnormalities

Question 44

What does the cochlear (VIIIc) nerve pass through?

Answer 44

Bony core of cochlea called modiolus