Anatomy and Histology of the Ear

Question 1

External ear is supplied by what artery

Answer 1

Posterior auricular from external carotid, as well as anterior auricular branches from superficial temporal

Question 2

Innervation to the external ear

Answer 2

Auriculotemporal to anterior external ear
Posterior ear supplied by lesser occipital and greater auricular
Vagus and glossopharyngeal nerve supply the concha/inner bowl of ear
Facial nerve supplies skin over mastoid process

Question 3

External acoustic meatus innervation

Answer 3

Superior TM supplied by facial
Anterior TM auriculotemporal
Posterior TM great auricular nerve
Inferior/floor of TM Arnolds nerve from vagus

Question 4

Cough reflex

Answer 4

Efferent- vagus and phrenic

Afferent- vagus

Question 5

Outer 2/3rds vs inner 2/3rds of EAC

Answer 5

Inner 1/3rd is only skin and bone (only place in body like that)
External 2/3rds have CT and cartilage

Question 6

Epithelium of TM

Answer 6

Outside layer is stratified squamous

Inside layer is simple cuboidal

Question 7

Where is the cone of light found in the TM

Answer 7

Inferior/2nd quadrant

Question 8

Tympanic cavity is located in what bone

Answer 8

In the petrous portion of temporal bone

Question 9

Chorda tympani runs over what in the middle ear

Answer 9

Runs over the tensor tympani

Question 10

Anterior, lateral walls and roof/floor of tympanic cavity

Answer 10

Anterior wall- Eustachian tube opening
Lateral wall- tympanic membrane
Floor- jugular wall
Roof- tegment tympani

Question 11

What sinus runs into tympanic cavity

Answer 11

Sigmoid sinus

Question 12

Distal 2/3rds and proximal 1/3rd of eustachian tube

Answer 12

Distal 2/3 are cartilage

Proximal 1/3 is bone

Question 13

What bone is associated with oval window

Answer 13

Stapes

Question 14

Membranous labyrinth

Answer 14

Made of small sacs and tubes within bony labyrinth
Contains cochlear duct and semicircular ducts with utricle and saccule
Contains sensory cells

Question 15

Bony labyrinth

Answer 15

Contains cochlea, vestibule and semicircular canals, separated from membranous labyrinth by perilymph

Question 16

Scala media

Answer 16

Middle compartment of cochlear duct, contains endolymph

Stria vascularis forms the lateral wall and creates endolymph

Question 17

Scala vestibuli

Answer 17

Contains perilymph, moved by stapes at oval window, continuous with scala tympani

Question 18

Scala tympani

Answer 18

Connected to round window

Question 19

Organ of corti composition

Answer 19

On floor of scala media resting on basilar membrane
Composed of hair cells, phalangeal cells (support for hair cells) and pillar cells (support b/w basilar membrane and tympanic lip)

Question 20

How does organ of corti function

Answer 20

Basilar membrane vibrates with sound causing deflection of stereocilia attached to tectorial membrane, opening K+ channels in hair cells

Question 21

Inner ear/middle functions

Answer 21

Inner-Responsible for balance, and takes external sound waves and transforms them into usable information for brain
Middle- takes sound waves and turns it into physical movement

Question 22

Path of sound waves in inner ear

Answer 22

Stapes moves oval window causing fluid pressure wave formation in perilymph
Wave distorts vestibular membrane causing pressure wave within endolymph of scala media
Basilar membrane is displaced, hair cells are distorted, pressure in perilymph is transferred to scala tympani and exits via round window

Question 23

Semicircular canals

Answer 23

Sense head rotations
Filled with endolymph
Connected to utricle
End of canals have ampulla with gelatinous-like cap called cupulla which has hair cells with stereocilia attached

Question 24

Utricle

Answer 24

Found inside vestibule
Contains a macula w/hair cells and stereocilia and an overlying otolithic membrane which is covered with calcium carbonate crystals called otoconia
Senses linear acceleration and head tilts in horizontal plane
Which way is forward? u trip forward

Question 25

Saccule

Answer 25

Also found inside vestibule and has a macule like the utricles
Senses acceleration and head tilts in vertical plane
Which way is up? sack up

Question 26

What causes depolarization of hair cells

Answer 26

K+ channels opening

Question 27

Hair cells and kinocilia

Answer 27

Hair cells have stereocilia and the grow in length in a row
Kinocilia is the longest one
If other cilia are deflected towards kinocilium, K+ channels open

Question 28

Perilymphatic space

Answer 28

Found between bony and membranous labyrinths
Similar composition to CSF
Drains via perilymphatic/cochlear duct into subarachnoid space
Originates from periosteum

Question 29

Endolymphatic space

Answer 29

High in K+, low in Na+
Originates from stria vascularis
Drains via endolymphatic duct into venous sinuses of dura mater

Question 30

What type of cartilage is in auricle, and what supplies it with nutrinets

Answer 30

Elastic cartilage, supplied by perichondrium

Question 31

What happens if perichondrium is sheared off elastic cartilage

Answer 31

Hematoma, necrotic cartilage
Necrotic cartilage results in chondrogenesis
Creates cauliflower ear

Question 32

What antibiotic should be avoided with TM injury

Answer 32

Gentamicin

Question 33

Mastoiditis

Answer 33

Infection of mastoid cells
Can spread into cranial fossa via petrosquamous cranial suture
Treated with abx

Question 34

Menieres syndrome

Answer 34

Associated with increased endolymph volume leading to abnormal signaling

Question 35

Conductive hearing loss

Answer 35

Effects outer or middle ear- otitis media, excessive wax, otosclerosis

Question 36

Sensorineural hearing loss

Answer 36

Reduction in sound level and/or fidelity due to damage to inner ear or auditory nerve
Affects hearing at different frequencies and intensities
Age related or noise induced

Question 37

Central hearing loss

Answer 37

Problem in CNS