Deafness in the Elderly Anatomy
To better understand presbycusis, it helps to understand the anatomy of the ear.
Sound travels through the air as waves. The external ear collects sound waves and funnels them into the ear canal. Inside the ear canal, the eardrum vibrates when sound waves strike the drum's surface. These vibrations cause tiny bones, called ossicles, to vibrate in the middle ear. The ossicles, in turn, transmit the vibrations to the cochlea in the inner ear.
The inside of the cochlea looks like a snail shell filled with fluid. Tiny hairs, called hair cells, line the inner wall of the cochlea. Vibrations from the ossicles pass through the fluid and stimulate the hair cells. The hair cells send electrical impulses to the brain, which interprets the information as sound.
The inner ear also contains the semi-circular canals, which also contain fluid and hair cells. The hair cells in the semi-circular canals sense the position of the body and send this information to the brain. This structure allows the body to maintain balance and equilibrium.
- Pinna: the cartilage and skin of the external ear
- Ear canal: passageway that leads to the eardrum
- Tympanic membrane: the eardrum
- Ossicles: three tiny bones that vibrate when sound waves strike the eardrum
- Inner ear, or labyrinth: includes the cochlea and semi-circular canals
- Cochlea: contains fluid and hair cells
- Semi-circular canals: contains fluid and hair cells
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