EYE AND EAR ANATOMY

Question 1

What 5 eye muscles are innervated by occulomotor nerve (CN III)

Answer 1

Dorsal, ventral, medial rectus; ventral oblique, retractor bulbi

Question 2

What are the 2 structures of the external ear

Answer 2

pinna and external acoustic meatus

Question 3

Blood supply of the external ear

Answer 3

external carotid a, external jugular v, maxillary v

Question 4

Middle ear regions & structures

Answer 4

Tympanic membrane (eardrum), tympanic cavity (oval window, cochlear window, tympanic bulla), & auditory ossicles (mallus,incus, stapes),

Question 5

Innervation of the middle ear

Answer 5

facial nerve

Question 6

innervation of external ear

Answer 6

Optic - sensory

Vestibulocochlear - motor

Question 7

Structure of the tympanic membrane

Answer 7

thin partition separating the lumen of the external acoustic meatus from the tympanic cavity

slanted and its surface area is larger than external acoustic meatus

medial surface is covered by the mucosa lining the tympanic cavity

Question 8

Function of the tympanic membrane

Answer 8

when a sound wave travels into the ear canal, the membrane vibrates and transmits vibrations to the auditory ossicles to reach the inner ear to covert mechanical movement to input in the brain

Question 9

Anatomy of the malleus

Answer 9

mandibrium and rostal process

Question 10

Anatomy of the incus

Answer 10

short and long crus, os lenticular

Question 11

Anatomy of the stapes

Answer 11

head and base

Question 12

What are the 2 muscles of the auditory ossicles

Answer 12

Tensor tympani & Stapedius

Question 13

Innervation of the tensor tympani

Answer 13

branch of the mandibular nerve

Question 14

Innervation of the Stapedius

Answer 14

Facial nerve

Question 15

acoustic reflex

Answer 15

involuntary muscle (tensor tympani and stapedius) contraction inhibiting the vibrations of the ossicles and reducing transmission of the sound in response to loud noise

Question 16

structure of the cochlea

Answer 16

spiral shaped structure that turns around modiolus bone

Question 17

Innervation of the cochlea

Answer 17

vestibulocholear (CN VIII)

Question 18

What are the 3 channels all running around the modiolus to the apex of the cochlea?

Answer 18

• scala vestibuli (upper most channel at the base of the cochlea)
• cochlear duct
• scala tympani (lowest channel under the cochlear duct)

Question 19

where does the scala tympani terminate?

Answer 19

secondary tympanic membrane

Question 20

Whats referred to as perilymph in the cochlea?

Answer 20

scala vestibuli & scala tympani

Question 21

Whats referred to as endolymph in the cochlea?

Answer 21

cochlear duct

Question 22

What is the function of the cochlea

Answer 22

receives sound waves in the form of vibrations which cause the stereocilia to move – stereocilia convert these vibrations into nerve impulses which are taken up in the brain to be interpreted

Question 23

what does the basement membrane do in the cochlea?

Answer 23

its different shape (thicker at the base and thinner at the apex) makes high frequency sounds travel far less than the low frequency sounds in the cochlea

Question 24

structure of the organ of corti (spiral organ)

Answer 24

lies within the cochlear duct of the cochlea

consists of sensory hair cells that rest on the basilar membrane – inner and outer hair cells

Question 25

function of the organ of corti

Answer 25

originate nerve impulses that are produced by the sounds received by the external ear

senses mechanical vibrations of incoming sounds and converts it to AP

Question 26

inner hair cell function (organ of corti)

Answer 26

need to vibrate to create AP – cilia on hair cells move and open up AP

Question 27

outer hair cell function (organ of corti)

Answer 27

sensitive to sounds causing vibration of hair cells –embedded in tectorial membrane

Question 28

Explain the anatomy of the vestibule

Answer 28

• 3 semicircular ducts which respond to the rotation of the head and has 3 crista ampullaris receptors
• Utriculus which responds to gravity and has 1 macula utriculi receptor
• Sacculus which responds to linear velocity and has 1 macula sacculi receptor

Question 29

What are the 3 types receptors of the vestibule

Answer 29

crista ampullaris (3 of them), macula utriculi (1), macula sacculi (1)

Question 30

Whats the function of the crista ampullaris receptors?

Answer 30

• contains gelatinous cupula thats heavier than endolymph
• around the gelatinous cupula is found the endolymph
• head rotation causes endolymph to move and gelatinous cupula deflects causing microvilli to move
• microvilli bends towards kinocilium stimulates the nerve
• microvilli bending away from kinocilium inhibits nerve endings

Question 31

How does input from the receptors of the vestibule travel?

Answer 31

Membranous labyrinth –> vestibular nerve –> vestibular nuclei –> vestibular spinal tract –> spinal cord, cerebellum, forebrain, reticular formation, extra ocular muscles

Question 32

Whats the function of the macula receptors?

Answer 32

• composed of neuroepithelium
• microvilli of the hair cells project into the gelatinous otolithic membrane which initiates inertia of the fluid due to the position of the head in the space

Question 33

What are the two parts of the inner ear?

Answer 33

Membranous labyrinth -contains endolymph whose movement inside the system stimulates sensory cells in the membranous walls

osseous labyrinth - filled with perilymph (CSF) that surrounds the membranous labyrinth as a water cushion

Question 34

What structures are associated with the Membranous labyrinth in the inner ear?

Answer 34

two enlargements in the middle of the Membranous labyrinth known as utriculus and sacculus

from the utriculus arises 3 semicircular ducts concerned with balance

from the sacculus arises the spiral cochlear duct which is concerned with hearing

Question 35

What are the non-auditory nerves of the middle ear?

Answer 35

sympathetic supply to head is the facial nerve – branch of the mandibular nerve

Question 36

What structures are associated with the osseous labyrinth in the inner ear?

Answer 36

bony capsule that houses the Membranous labyrinth, vestibule, semicircular canal, ampullae, and cochlea