Changing altitudes cause a changing air pressure within the surrounding air. This changing air pressure can cause difficulties hearing and even pain. The role of the Eustachian tube is to equalise the pressure between the outer and inner ear thus reducing the pressure on the ear and allowing easier hearing to occur pain free. The Eustachian tube connect the inner ear to the outside of the pharynx and opens its canal briefly when a yawn, cough or swallow occurs. When the canal is opened it equalises the pressure between the inner and outer ear.

Figure 19.1 represent the location of the Eustachian tube and its process of equalising pressure.

Aubusson, Eileen Kennedy Peter. Biology in Context: the Spectrum of Life. Victoria : Oxford Uni. Press., 2001. Print.
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