The Inner Ear

Question 1

Functions of the inner ear?

Answer 1

Covert mechanical signals from the middle ear into electrical signals which can transfer info to the auditory pathway in the brain Also maintains balance by detecting position and motion

Question 2

Position of the inner ear?

Answer 2

Located within the petrous part of the temporal bone Between middle ear and internal acoustic meatus

Question 3

What is the bony labyrinth?

Answer 3

Bony cavities within the petrous part of the temporal bone Comprised of -cochlea -vestibule -three semicircular canals

Question 4

What are each of the structures of the bony labyrinth lined with?

Answer 4

Internally with periosteum

Contain a fluid called perilymph

Question 5

Describe the membranous labyrinth component of the inner ear

Answer 5

Lies within the bony labyrinth

Consists of the cochlear duct, semicircular ducts, utricle and saccule

Filled with fluid - endolymph

Question 6

What are two openings of the inner ear into the middle ear?

Answer 6

The oval window between the middle ear and the vestibule (stapes attaches to it)

The round window between the middle ear and the scala tympani

Question 7

Describe the vestibule of the bony labyrinth

• what it has
• what it communicates with
• what is in it

Answer 7

The central part

Has the oval window

Communicates anteriorly with the cochlear and posteriorly with the semicircular canals

Utricle and saccule of membranous labyrinth are within it

Question 8

What is within the cochlea of the inner ear?

Answer 8

Cochlear duct of the membranous labyrinth - the auditory part of the inner ear

Question 9

What does the cochlea twist around?

Answer 9

Modiolus

Question 10

Branches from which nerve are found at the base of the modiolus?

Answer 10

Vestibulocochlear nerve

Question 11

What extends outwards from the modiolus, holding the cochlear duct in position?

Answer 11

Spiral lamina

Question 12

What are the two perilymph fluid-filled chambers above and below the cochlear duct?

Answer 12

Scala vestibuli - supeiorly. Continuous with the vestibule

Scala tympani - Inferior to the duct. Terminates at the round window

Question 13

How many semicircular canals are there?

What are they called?

Function?

Answer 13

Three

Anterior, lateral and posterior

Responsible for balance, along with the utricle and saccule

Question 14

What is the swelling at one end of each semicircular canal called?

Answer 14

Ampulla

Question 15

What is the membranous labyrinth?

Where is it?

What surrounds it?

Answer 15

Continuous system of ducts filled with endolymph.

Lies within the bony labyrinth

Surrounded by perilymph

Question 16

Which structures make up the membranous labyrinth?

Answer 16

Cochlear duct

Three semicircular ducts

Saccule and utricle

Question 17

What are the walls of the cochlear duct formed from?

Answer 17

Lateral: Thickened periosteum, known as the spiral ligament

Roof: A membrane which separates the cochlear duct from the scala vestibuli - Reissner’s membrane

Floor: Membrane whih separates the cochlear duct from the scala tympani - basilar membrane

Question 18

What is in the basilar membrane?

Answer 18

The epithelial cells of hearing - the Organ of Corti

Question 19

What are and where are the saccule and utricle?

Answer 19

Two membranous sacs located in the vestibule

Question 20

Which ducts do the utricle and saccule receive?

Answer 20

Utricle - semilunar ducts

Saccule - cochlear duct

Question 21

How is balance detected?

Answer 21

Endolymph within the semicircular ducts changes speed or direction when the head is moved.

Sensory receptors in the ampullae of the canals detect the change, and send signals to the brain.

Question 22

What drains endolymph?

Answer 22

The endolymphatic duct from the saccule and utricle

Question 23

What is Meniere’s disease?

Answer 23

A disorder of the inner ear, characterised by episodes of vertigo, low pitched tinnitus and hearing loss.

Question 24

What is thought to cause the symptoms of Meniere’s disease?

Answer 24

Excess accumulation of endolymph within the membranous labyrinth, causing progressive distension of the ducts.

Resulting pressure fluctuations damage the thin membranes of the ear that detect balance and sound

Question 25

Arteries supplying the bony labyrinth?

Answer 25

Anterior tympanic branch from maxillary artery

Petrosal branch from the middle meningeal artery

Stylomastoid branch from the posterior auricular artery

Question 26

Arterial supply the membranous labyrinth?

Answer 26

Labyrinthine artery, a branch of the inferior cerebellar artery aka basilar artery

Divides into three branches

-cochlear supplying the cochlear duct

-2 vestibular branches supplying the vestibular apparatus

Question 27

Venous drainage of the inner ear?

Answer 27

Labyrinthine vein, empties into the sigmoid sinus aka inferior petrosal sinus

Question 28

Inner ear innervation?

Answer 28

Vestibulocochlear nerve (CN VIII)

Branches into the vestibular nerve (balance) and cochlear nerve (hearing)

Question 29

Through which structure does the vestibulocochlear nerve enter the inner ear?

Answer 29

Internal acoustic meatus

Question 30

Which other nerve passes through the inner ear but does not innervate anything?

Answer 30

Facial nerve

Question 31

What does the vestibular nerve innervate?

Answer 31

Enlarges to form the vestibular ganglion, then splits into superior and inferior parts

Utricle, saccule and semicircular ducts

Question 32

What does the cochlear nerve innervate?

Answer 32

Enters at base of modiolus and its branches pass through the lamina to supply the receptors of the Organ of Corti