How We HearThe human ear is an intricate and delicately balanced structure of the body. In order to understand hearing loss, it is important to know how a normally functioning ear works.
The ear is divided into three parts: outer ear, middle ear and inner ear.
Outer EarThe function of the outer ear (pinna) is to collect sound vibrations and funnel them through the ear canal to the eardrum (tympanic membrane). The outer two-thirds of the pinna is lined with cartilage, and contains sebaceous and wax glands. The wax prevents foreign objects from traveling down the canal. Old wax is expelled as new wax is produced.
Middle EarThe middle ear is an air-filled space containing the three smallest bones in the human body. These bones, called ossicles (also known as the hammer, anvil and stirrup), vibrate along with the eardrum. These vibrations amplify and are transmitted across a tiny membrane into the snail-shaped inner ear (cochlea).
An important component of the middle ear is the eustachian tube, which connects the middle ear to the back of the nose. Its function is to control air pressure and bring a fresh oxygen supply to the lining of the middle ear.
Inner EarThe inner ear contains structures for both hearing and balance. When sound waves reach the inner ear, they enter the cochlea. Fluid in the cochlea stimulates 25,000 tiny nerve endings, or "hair cells," to move. As these hair cells move, they send electrical nerve impulses to the brain along the auditory nerve. The brain interprets these signals as sound information.
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