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What is the Eustachian tube?
The Eustachian tube originates in the rear of the nose adjacent to the soft palate, runs a slightly uphill course, and ends in the middle ear space. The middle ear space is the hollowed out portion of the skull bone that contains the hearing apparatus and is covered on one side by the eardrum. In adults, the Eustachian tube is approximately 35 mm long (1.3 inches) and approximately 3 mm in diameter (less than 1/10 inch). Cartilage provides the supporting structure for the first two-thirds of the Eustachian tube, with the last third (the part closest to the middle ear space) being made of bone.
The tissue that lines the Eustachian tube is similar to that inside the nasal cavity and may respond the same way (swelling) when presented with similar stimuli. The Eustachian tube was named in honor of the 16th century Italian anatomist Eustachius. Sources credit Almaceon of Sparta as the first to describe the structure in approximately 400 BC.
What are the functions of the Eustachian tube?
The primary function of the Eustachian tube is to ventilate the middle ear space, ensuring that its pressure remains at near normal environmental air pressure. The secondary function of the Eustachian tube is to drain any accumulated secretions, infection, or debris from the middle ear space. Several small muscles located in the back of the throat and palate control the opening and closing of the tube. Swallowing and yawning cause contractions of these muscles located in the back of the throat and help regulate Eustachian tube function. If it were not for the Eustachian tube, the middle ear cavity would be an isolated air pocket inside the head that would be vulnerable to every change in air pressure and lead to unhealthy middle ear space function.
Normally, the Eustachian tube is closed, which helps prevent the inadvertent contamination of the middle ear space by the normal secretions found in the back of the nose. A dysfunctional Eustachian tube that is always open is called a "patulous" Eustachian tube. Patients with this rare condition are plagued by chronic ear infections. A much more common problem is a failure of the Eustachian tube to effectively regulate air pressure. Partial or complete blockage of the Eustachian tube can cause sensations of popping, clicking, and ear fullness and occasionally moderate to severe ear pain. Such intense pain is most frequently experienced during sudden air pressure changes during airplane travel, particularly during take-off and landing. Young children may describe the popping sensation as "a tickle in my ear."
As Eustachian tube function worsens, air pressure in the middle ear falls, and the ear feels full and sounds are perceived as muffled. Eventually, a vacuum is created which can then cause fluid to be drawn into the middle ear space (termed serous otitis media). If the fluid becomes infected, the common ear infection (suppurative otitis media) develops.