The Eustachian tube
The Eustachian tube, also auditory tube or pharyngotympanic tube is a tube that links the nasopharynx to the middle ear. It is a part of the middle ear. In adult humans the Eustachian tube is approximately 35 mm long. It is named after the sixteenth-century anatomist Bartolomeo Eustachi. Some modern medical books call this the pharyngotympanic tube
Eustachian tube functions – pressure equalization
Under normal circumstances, the human Eustachian tube is closed, but it can open to let a small amount of air through to prevent damage by equalizing pressure between the middle ear and the atmosphere. Pressure differences cause temporary conductive hearing loss by decreased motion of the tympanic membrane and ossicles of the ear.
Various methods of ear clearing such as yawning, swallowing, or chewing gum, may be used intentionally to open the tube and equalize pressures. When this happens, humans hear a small popping sound, an event familiar to aircraft passengers, scuba divers, or drivers in mountainous regions
Eustachian tube function – mucus drainage
The Eustachian tube also drains mucus from the middle ear. Upper respiratory tract infections or allergies can cause the Eustachian tube, or the membranes surrounding its opening to become swollen, trapping fluid, which serves as a growth medium for bacteria, causing ear infections. This swelling can be reduced through the use of nasal sprays.
Ear infections are more common in children because the tube is horizontal and shorter, making bacterial entry easier, and it also has a smaller diameter, making the movement of fluid more difficult. In addition, children’s developing immune systems, and poor hygiene habits make them more prone to upper respiratory infections.
Middle ear disorders
Otitis media
- Inflammation of the middle ear
- Children under 7 are more susceptible to this condition because the Eustachian tube is shorter and at more of a horizontal angle than in the adult ear
- Many children’s middle ear disorders are related to the Eustachian tube
Barotrauma
- Barotitis, a form of barotrauma, may occur when there is a substantial difference in air or water pressure between the outer inner and the inner ear
- For example in a rapid ascent while scuba diving, or a sudden decompression of an aircraft at high altitude
Eustachian tube dysfunction
- Some people are born with a dysfunctional Eustachian tube, which is much slimmer than the usual human Eustachian tube
- This may be genetic, but it has also been suggested to be a condition in which the patient did not fully recover from the effects of pressure on the middle ear during birth (retained birth compression)
- This disorder may result in a large amount of mucus accumulating in the middle ear, often impairing hearing to a degree
- This condition is associated with otitis media with effusion, and may result in the mucus becoming very thick and glue-like, a condition known as glue ear
- Smoking can also cause damage to the cilia that protect the Eustachian tube from mucus, which can result in the clogging of the tube and a buildup of bacteria in the ear, leading to a middle ear infection in some cases
- Eustachian tube dysfunction can be caused by recurring and chronic cases of sinus infection – this results from excessive mucus production which causes obstruction to the openings of the Eustachian tubes
Patulous Eustachian tube
A patulous Eustachian tube is a rare condition, in which the Eustachian tube remains intermittently open, causing an echoing sound of the person’s own heartbeat, breathing, and speech.
This may be temporarily relieved by moving into a position where the head is upside down.