Eustachian tubes are small passageways on either side of the head that connect the back of the throat, or the pharynx, to the middle ear. Sometimes, these passages are referred to as pharyngotympanic tubes, but the term Eustachian is still more common and recognizable by those without a medical background. These tubes were named in honor of the scientist, Bartolomeo Eustachius, who studied the ear in the 16th century and defined its components with greater precision than had been accomplished before.
Among other things Eustachius and scientists have discovered since his time, is that the Eustachian tubes are about 1.5 inches (3.81 cm) long in adults. One of their more interesting features is that they remain closed most of the time, but they open to keep pressure values consistent between the middle ear and the throat.
As the tubes open, they can sometimes cause a small popping noise. Most people are fairly familiar with this noise if they travel by air or climb tall mountains. The pop can bring relief as pressure built up in the middle ear can become uncomfortable.
In order to force the tubes to open, people often chew gum or try to yawn. Yawning does tend to open the tubes, as does opening the mouth wide, as it stretches the muscles in the neck. The tubes also open slightly during colds and allergies to drain mucus from the ears into the pharynx. If the mucus hardens or the Eustachian tubes become swollen, however, fluid cannot drain properly and may accumulate and grow bacteria in the middle ear, causing ear infections.
One of the reasons that children are more prone to ear infections is because their Eustachian tubes are shorter and also are more horizontal to the nose and throat. In adult ears, they normally point downward toward the throat, which allows for easier drainage, since simple gravity does some of the work. The horizontal position in children means that there is very little downward flow, which can cause a back up of mucus and lead to middle ear infections.
In some instances, the failure of the Eustachian tubes to properly drain causes ear infections with such frequency in children that they have tubes placed in their ears to keep the passageway open. This allows for easier drainage and frequently ends bouts of ear infection. As a child ages, the tubes tend to fall out because the passageway to the throat has been naturally widened.