The ear and how it works - Action On Hearing Loss: RNID
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The ear and how it works

Please install the Flash Plugin As well as being your organs of hearing, ears are also part of the mechanism that controls your balance.

Your ears have three sections: the outer ear, the middle ear and the inner ear.

Outer ear

The outer ear consists of the pinna, which is the part you can see on the side of your head, and the external auditory canal, which is the passage along which sound travels.

Middle ear

The middle ear is a space or cavity about 1.3 centimetres (cm) across that is filled with air. The cavity is connected to your nose and throat by the eustachian tube.

A chain of three tiny bones called the ossicles stretches right across the middle ear cavity to conduct sound from the eardrum through to the inner ear. These bones are called the malleus, the incus and the stapes.

When sound enters your ears and makes the eardrum vibrate, the vibrations pass from the eardrum along the ossicles.

Inner ear

The inner ear has two parts: the cochlea and the semicircular canals.

  1. Cochlea

    The cochlea – the hearing part – is a coiled spiral tube about 3.5cm long. The spiral contains two fluid-filled chambers; an outer and an inner one. The inner chamber contains the organ of corti. This has about 17,000 small hair cells, and each one has tiny hair-like structures called stereocilia, which project into the cochlear fluid.

    When sound waves enter the cochlea the stereocilia move, triggering an electrical pulse in the auditory nerve. The nerve passes electrical impulses to your brain, which recognises them as different sounds.

  2. Semi-circular canals

    The semicircular canals are not used for hearing. They are part of your balance system. They are filled with fluid and have hair cells that project stereocilia, rather like those in the cochlea. They give your brain information about the direction your head is moving.

You can find out more information in our Ears and ear problems factsheets section and from the Action on Hearing Loss Library, which is the largest library in Europe on deafness and hearing loss.

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