The Outer Ear
The outer ear includes the Auricle (or pinna), the External Auditory Canal and the Eardrum. It channels sounds from the surrounding environment into the hearing system. The auricle helps to gather the sound waves and the auditory canal then directs them to the eardrum.
The Middle Ear
The middle ear is an air-filled cavity which contains the smallest bones in the human body - the Malleus, Incus and Stapes. These are connected to the eardrum on one side, and on the other side to a thin membrane-covered opening on the wall of the inner ear. The middle ear is also connected to the throat via the Eustachian Tube which keeps the air pressure in the middle ear equal to that of the surrounding environment.
The Inner Ear
In the inner ear sound is processed by the Cochlea, while information affecting balance is processed by the Semicircular Canals. Along the entire length of the Cochlea, which is fluid-filled, there are tiny hair cells. When the fluid in the Cochlea is displaced by sound waves that have been passed on through the action of the middle ear bones, the hair cells bend. This triggers a chemical response which activates the corresponding nerve endings. These then transmit the message to the area of the brain in charge of processing and interpreting auditory input.
