The ears are responsible for hearing sounds and for balance in the human body. The ear has three parts – the outer, middle and inner ears.

Outer ear

The outer ear collects sounds from the environment and funnels them through the auditory system.

This structure is also known as the pinna and is made of cartilage. It collects invisible sound waves from the environment funnelling them into the outer ear. The sound waves are guided down your ear canal towards the ear drum.

The ear drum or tympanic membrane resembles a flexible window that vibrates as sound waves bounce on it.

Middle ear

The middle ear transmits sound from the outer ear to the inner ear

This is a hollow, air-filled space also known as the tympanic cavity. It connects to the back of the throat and nose through the Eustachian tubes.

Ear drum vibrations continue into the middle ear where the 3 smallest bones in the human body are found. These are also known as the auditory ossicles – the hammer (malleus), anvil (incus) and stirrups (stapes) – named because of their shapes.

The main function of these bones is sound amplification. Sound waves make them vibrate, causing sound to be transmitted to the inner ear.

Inner ear

The inner ear is responsible for interpreting and transmitting sound (auditory) sensations and balance (vestibular) sensations to the brain.

This is found in the temporal bone of the head and is made up of 3 related parts – the cochlea (or spiral tube), 3 semicircular canals and the vestibule (labyrinth).

The cochlea is responsible for hearing. It contains tiny hair-like cells connected to the acoustic nerve. This nerve changes energy vibrations in the inner ear fluid into nerve impulses that go to the brain. The brain interprets the impulses received to identify what you are hearing.

The vestibule and 3 semicircular canals are responsible for balance. These canals are arranged at right angles to each other. If you change the position of your head, the fluid in the canals moves, allowing the brain to determine the amount and direction of movement.

Useful link

View an animation of hearing from the BBC website.

    Published 1 February 2011