Function Of Normal Ear

The ear is divided into three parts: external ear, middle ear, and inner ear.  Each part performs an important function in the process of hearing and balance.

The external ear consists of an auricle and the ear canal.  These structures gather sound and direct the sound towards the eardrum membrane. 

The middle ear chamber lies between the external ear and the inner ear and consists of an eardrum membrane and three small ear bones (ossicles): malleus (hammer), incus (anvil), stapes (stirrup).  These structures transmit sound vibrations to the inner ear.  In so doing they act as a transformer, converting sound vibrations in the external ear canal into fluid waves in the inner ear.

The inner ear chamber (labyrinth) contains both the auditory (hearing) and vestibular (balance) mechanisms and is filled with fluid.  The auditory chamber is called the cochlea.  This term is derived from Latin and means snail shell, which the cochlea resembles.

Fluid waves initiated by movement of the three small ear bones are transmitted to the cochlea where they in turn stimulate the delicate hearing cells (hair cells) of which there are over sixteen thousand.  Movements of these hair cells generate an electrical current in the auditory nerve.  This current is transmitted, through various complicated interconnections in the brain stem, to that portion of the brain (auditory cortex) which recognizes these electrical stimulation as sound.  Movement of fluid in the balance chambers (vestibule and three semicircular canals) similarly result in electrical impulses which are interpreted in the brain as motion.  Balance is maintained by the interaction and coordintion in the brain of nerve impulses from the inner ear, eyes, neck muscles and the muscles and joints in the limbs.  A disturbance in any of these areas may result in the subjective sensation of dizziness or unsteadiness.

Hence the ear has a dual function of hearing perception and maintaining balance of the body.