More information about the ear

The vibrations are transmitted by a series of bones - the Malleus, the Incus and the Stapes - called the Ossicles, through the middle ear to an oval window at the entrance to the inner ear, which is contained within the base of the skull. This arrangement means the vibrations of the eardrum are magnified 16 times by the time they reach the oval window. The space between the eardrum and the oval window is the middle ear. In order that the eardrum can vibrate it is important that the pressure in the middle ear is the same as in the canal. To allow this to happen there is a tube from the middle ear, called the Eustachian tube, which runs to the back of the throat. It is this tube which opens when we yawn or swallow and gives the sensation that the ear is popping. Behind the ear, and connected to the middle ear, is the mastoid bone which contains air cells.

The inner ear contains fluids whose movement is detected by a number of cells called hair cells, held in an organ called the cochlea. These convert movement into electrical currents which are then transmitted along the auditory nerve.

Babies can normally hear from birth, and hearing ability develops rapidly during the first year of life, so that by nine months they are very fond of their own babbling, and by 1 year will usually respond to familiar words, such as bye-bye. Different disease processes affect hearing in different ways.

The inner ear also contains the organs of balance. There are three semi-circular canals - the labyrinth - which are at right angles to each other, and an organ called the vestibule. The vestibule responds to movement in a linear direction. The semi-circles contain cells which move as we move our heads round or up and down. Disturbances of the action of the cells causes a sensation of dizziness. Information from the cells, coupled with information from our eyes, and other information from our joints, is integrated in the brain in order that we know our orientation in relation to the environment around us. We need information from all three sources to keep our balance. (Try standing on one foot. Now close your eyes).