This 3-4 cm tubular structure connecting the nose with the middle ear permits communication between the inner ear and the external atmosphere so that equal pressure is maintained on either side of the eardrum. The passage can be opened up by swallowing in order to equalize a difference between internal and external pressure. When the tube becomes blocked due to swelling of its mucous membrane lining, the air in the middle ear is absorbed and replaced by fluids that prevent the eardrum from vibrating in response to sound waves. The tube may also serve as a pathway to the ear for infections of the throat. A common ear disease known as Otitis media, usually appearing in early childhood, is thought to be related to the Eustachian tube. The tube tends to be shorter and more horizontal among children, factors which facilitate the spread of infections from upper respiratory diseases to the middle ear, as well as the accumulation of fluids in the region.
The term Eustachian tube was introduced by the Italian anatomist Antonio Maria Valsalva (1666-1723), professor of Anatomy at Bologna. It was first described by Alcmaeon of Croton, about 500 B.C.
- B. Eustachi:
Epistola de auditus organis. 1562. Opuscula anatomicae. Venetiis, V. Luchinus, 1564.