Ears
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What are the THREE regions of the ear?
External, Middle & Inner.
What does the External ear consist of?
Pinna, External auditory canal, Tympanic membrane.
What does the Middle ear consist of?
THREE ossicles, Eustachian/Auditory tube, Oval & Round window.
What does the Inner ear contain?
The Vestibule, The Cochlea, Semicircular canals.
What is the function of the External ear?
-Pinna directs sound waves toward the Tympanic membrane, -External auditory canal contains ceruminous glands which excrete cerumen to protect and lubricate the external ear. -Tympanic membrane is vibrated by sound waves & transfers to the ossicles.
What is the function of the Middle ear?
-The THREE ossicles transmit & amplify sound waves, -Auditory tube leads to the Nasopharnx and assists to equalise pressure on both sides of the Tympanic membrane.
What are the THREE ossicles?
Malleus, Incus, Stapes.
What separates the External ear from the Middle ear?
The Tympanic membrane.
What separates the Middle ear from the Inner ear?
The Oval & Round windows.
What are the TWO main divisions of the Inner ear?
The Bony labyrinth & the Membranous labyrinth.
What does the Bony labyrinth contain?
Perilymph & the Membranous labyrinth.
What does the Membranous labyrinth contain?
Endolymph.
What is the function of Perilymph & Endolymph?
Both liquids conduct sound & respond to mechanical forces during changes in the body position.
What is the Cochlea?
A small snail shaped organ which contains receptors for hearing.
What are the THREE channels of the Cochlea?
Scala Vestibuli, Cochlea duct/Scala media, Scala Tympani.
Where the Scala vestibuli & the Scala tympani found? and what do they contain?
Both are located inside the Bony labyrinth and both contain Perilymph.
Where is the Cochlea duct/Scala media found? and what does it contain?
Found in the Membranous labyrinth and contains Endolymph.
What are the TWO membranes of the Cochlea duct?
Upper membrane: Vestibular membrane, Lower membrane: Basilar membrane.
What is found resting on the Basilar membrane?
A spiral organ known as the Organ of Corti - the organ of hearing.
State the physiology of hearing in order- The process of hearing.
1- Sound waves vibrate the Tympanic membrane, vibration passes onto the Ossicles. 2- Vibration of Ossicles transfers & amplifies vibratory motion to the Oval window, 3- Pressure waves are created in the Perilymph of the Cochlea, 4- Pressure waves travel through Perilymph & pass through the Vestibular membrane into the Endolymph. 5- Pressure waves in the Endolymph cause the Basilar membrane to vibrate which moves the hair cells. This creates an action potential if the threshold is met.
Which area of the Cochlea detects HIGH pitch sounds?
The base of the Cochlea.
Which area of the Cochlea detects LOW pitch sounds?
The apex of the Cochlea.
How is the volume of sound determined?
Loudness is determined by the intensity of sound waves. Loud noises stimulate more hairs & generate more impulses.
What is the function of the Vestibulocochlear nerve?
Carries impulses from the Vestibule & Organ of Corti. Starts as two seperate branches- Vestibular & Cochlear. Action potentials travel to the primary auditory area via the Cochlear branch of the Vestibulocochlear nerve.