Medical Definition of Eustachian tube
Eustachian tube: The tube that runs from the middle ear to the pharynx. The function of the Eustachian tube is to protect, aerate, and drain the middle ear and mastoid. The Eustachian tube permits the gas pressure in the middle ear cavity to adjust to external air pressure. When you are descending in an airplane, the Eustachian tube opens when your ears 'pop.' It is harder to get air into the middle ear than get it out, which is why we have more trouble with our ears when a plane is descending than when it takes off. Occlusion of the Eustachian tube can lead to the development of middle ear infection (otitis media). The Eustachian tube opens into the nasopharynx. The Eustachian tube measures only 17 to 18 mm, and it is horizontal at birth. As it grows to double that length, it grows
Last Editorial Review: 5/13/2016
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