a) The outer ear

The outer ear includes the auricle, the auditory canal and the eardrum. It funnels 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.

b) 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.

c) The inner ear

In the inner ear the auditory input is processed by the cochlea, while information affecting balance is processed by the semicircular canals. Along the entire length of the fluid filled cochlea there are tiny hair cells. These hair cells are bent when the fluid is displaced by sound waves passed on by the middle ear bones. 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 interpreting auditory input.