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Flashcards in The Inner Ear Deck (32):

Functions of the inner ear?

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


Position of the inner ear?

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


What is the bony labyrinth?

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


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

Internally with periosteum

Contain a fluid called perilymph


Describe the membranous labyrinth component of the inner ear

Lies within the bony labyrinth

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

Filled with fluid - endolymph



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

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


Describe the vestibule of the bony labyrinth

-what it has

-what it communicates with

-what is in it

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



What is within the cochlea of the inner ear?

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


What does the cochlea twist around?



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

Vestibulocochlear nerve


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

Spiral lamina


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

Scala vestibuli - supeiorly. Continuous with the vestibule

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



How many semicircular canals are there?

What are they called?



Anterior, lateral and posterior

Responsible for balance, along with the utricle and saccule



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



What is the membranous labyrinth?

Where is it?

What surrounds it?

Continuous system of ducts filled with endolymph. 

Lies within the bony labyrinth

Surrounded by perilymph


Which structures make up the membranous labyrinth?

Cochlear duct

Three semicircular ducts

Saccule and utricle


What are the walls of the cochlear duct formed from?

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


What is in the basilar membrane?

The epithelial cells of hearing - the Organ of Corti


What are and where are the saccule and utricle?

Two membranous sacs located in the vestibule


Which ducts do the utricle and saccule receive?

Utricle - semilunar ducts

Saccule - cochlear duct


How is balance detected?

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.


What drains endolymph?

The endolymphatic duct from the saccule and utricle


What is Meniere's disease?

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


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

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


Arteries supplying the bony labyrinth?

Anterior tympanic branch from maxillary artery

Petrosal branch from the middle meningeal artery

Stylomastoid branch from the posterior auricular artery


Arterial supply the membranous labyrinth?

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


Venous drainage of the inner ear?

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


Inner ear innervation?

Vestibulocochlear nerve (CN VIII)

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


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

Internal acoustic meatus


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

Facial nerve


What does the vestibular nerve innervate?

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

Utricle, saccule and semicircular ducts


What does the cochlear nerve innervate?

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