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The Eustachian Tube
To understand the Eustachian tube one must understand the middle ear and its function. The middle ear is a sealed, air filled cavity which gives the eardrum the ability to move easily, a property we call compliance. Compliance means that the eardrum moves or vibrates easily with little effort. Compliance gives the eardrum the ability to gather sound efficiently. The Eustachian tube is a selective valve that allows air to enter behind the sealed eardrum. The Eustachian tube connects the back of the nose to the middle ear. Air can pass from the back of the nose to the middle ear through the Eustachian tube (see diagram above). The Eustachian tube replaces the air the body absorbs from the middle ear. The Eustachian tube also equalizes the pressure changes in the outside air. This is what causes the "popping" that people describe when going up or down in the mountains or an airplane. The ability to "pop" the ears is very beneficial. Have you noticed that hearing is worse just before your ears pop? This is because of the property called compliance. If the air pressure is not equal on both sides of the eardrum, the ear drum will not move or vibrate efficiently (reduced compliance). The Eustachian tube maintains the optimal compliance by keeping the air pressure outside the ear the same as air pressure inside the ear. The end result is that the Eustachian tube preserves and maintains optimal hearing. Malfunction of the Eustachian tube can lead to many problems with the ears. For more information on these problems see: Fluid behind the ear drumEarache and ear infectionCholesteatoma and chronic infection
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