The Sense Of Hearing

• The ear is the sensory organ of sound.
• The sense of hearing is sensitive to the sound stimuli.
• The human ear can be divided into three main parts. These are known as the outer ear, the middle ear and the inner ear.
• Every structure of the ear has their own functions and are very important.

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Outer Ear

Structure	Function/Explanation
Pinna	Made of cartilage and skin and shaped like a funnel. It collects and directs sounds into the ear canal.
Ear canal	A long tube lined with hairs. It directs sounds to the eardrum.

Middle Ear

Structure	Function/Explanation
Eardrum	A thin membrane that seperates the outer ear from the middle ear. It vibrates and transmits sound waves to the ossicles.
Ossicles	Made up of three small bones which is the hammer, the anvil and the stirrup. It intensifies the vibrations of the sound waves by 22 times before transmitting to the oval window.
Eustachian tube	A narrow tube that joins the middle ear to the throat that balances the air pressure at both sides of the eardrum.
Oval window	An oval-shaped, thin membrane between the middle ear and the inner ear. It transmits sound vibrations from the middle ear to the inner ear.

Inner Ear

Structure	Function/Explanation
Cochlea	Filled with liquid and contains the ends of nerve cells. The vibration of the oval window causes this liquid to vibrate. The vibration is detected by the nerve cells and are then changed into impulses.
Auditory nerve	It carries the impulses to the brain which then interprets the impulses as sound.
Semicircular canals	For body balance.

Credit: http://pmr-science.wikispaces.com/1.5+The+Sense+of+Hearing