What are the Eustachian tubes or pharyngotympanic tubes?

The tuba or pharyngotympanic tubepharyngotympathetic tube, pharyngeal tube or auditory tubeis a tube connects the nasopharynx to the middle ear. There are two, one in each ear, and for a long time the name of Eustachian tubea name that is still widely used, especially colloquially.

In humans and many other land animals, the middle ear is made up of a air filled chamber, but this chamber is not in direct contact with the atmosphere through the ear canals; In the human case, the outer ear and the middle ear are separated by a membrane, the eardrumand the pharyngotympanic tube is the one that controls the flow of air connecting the middle ear with the back of the nasopharynx.

Normally, the pharyngotympanic tube is collapsed and prevents the passage of air but it opens in some circumstances, for example with swallowing or when subjected to a pressure difference between the interior of the middle ear chamber and atmospheric pressure. The objective is equalize the pressure between inside and outside to prevent damage to the structures of the ear. In addition, equalizing the pressure allows the correct transmission of sound waves to the chain of ossicles.

For example, as altitude increases (plane, road, etc.), atmospheric pressure decreases and the air in the middle ear expands, causing the pharyngotympanic tubes to open to let air out into the pharynx and release pressure. When the pressure decreases, the reverse happens, the air in the middle ear contracts and the pressure opens the pharyngotympanic tubes so that more air can arrive.

anatomy and structure

The pharyngotympanic tubes develop from the first embryonic pharyngeal pouch. During embryogenesis, the first pharyngeal pouch forms the tubotympanic recess that in its distal end will form the tympanic cavity and in the proximal part will give rise to the Eustachian tubes.

The pharyngotympanic tube is tubular in shape with an average length in adults of 3.5 to 4 cm. It starts from the anterior wall of the middle ear and ends at the lateral wall of the nasopharynx, approximately at the level of the inferior nasal concha, with a downward slope. The interior of the tube is lined with mucous membrane made up of ciliated pseudostratified columnar epithelium.

Its structure consists of bone, cartilage, and associated muscles. The bony part is closest to the middle ear; It goes from the anterior wall of the tympanic cavity to the rock of the temporal bone where the cartilaginous part is anchored. The cartilaginous part is the longest, about 2/3, and is made up of fibrocartilage which is attached on one side to the bony part and on the other to the mucosa of the nasal part of the pharynx.

There are four muscles involved in the function of the pharyngeal tubemainly the levator veli palatini and the tensor veli palatini. Contraction of these muscles opens the pharyngotympanic tubes automatically when swallowing. The salpingopharyngeus muscle and the tensor tympani may also be involved.

Function

The pharyngotympanic tubes have two main functions: balance pressure inside the tympanic cavity and drain mucus of the middle ear.

Under normal conditions, the pharyngotympanic tubes are closed but can be opened to allow small amounts of air to pass through and for atmospheric pressure and pressure inside the tympanic cavity to equilibrate.

When the pressures are not compensated, the tympanic membrane loses mobility, which means that the sound waves are not transmitted normally to the chain of ossicles and hearing loss. It is a sensation often described as "clogged ears."

Middle ear pressure imbalance typically occurs with altitude changessuch as when traveling by plane, on roads in mountainous areas, or when Diving. Yawning, swallowing, chewing, or trying to blow with your nose and mouth closed can help the pharyngotympanic tubes to open and the pressures to balance. If the imbalance is very pronounced, as can happen when diving, the tympanic membrane can become damaged.

Drainage of mucus from the middle ear is very important to control the possibility of infection; if the mucus is retained, microorganisms can establish themselves and grow.

medical implications

The pharyngotympanic tubes are implicated in various health problems and medical conditions. The most common is otitis media (inflammation of the middle ear) which is due in most cases to infections caused by inefficient drainage and ventilation, a key role of the Eustachian tubes.

In children, the pharyngotympanic tubes are shorter and less inclined, and the drainage is usually less than in adults, which is why otitis media is more common in children. It is also frequently associated with upper respiratory diseases that can cause the mucosa around the opening of the Eustachian tubes in the nasopharynx to swell and prevent them from opening correctly.

Some conditions, like smoking and chronic sinusitis, increase the possibility of otitis by affecting the function of the Eustachian tubes. Also the congenital dysfunction of the pharyngotympanic tubesboth for genetic reasons and due to pressure during childbirth or other non-genetic reasons, can favor otitis media, generally exudative or effusive otitis media.

Another lesion that occurs relatively frequently in the middle ear and that is related to the function of the pharyngotympanic tubes is the barotitis, a type of barotrauma. A barotrauma is tissue injury caused by a high pressure difference between an internal gas-containing space and the surrounding gas or fluid. In the middle ear it is common especially in divers who make an ascent too fast or in rapid decompression in flights.

The patulous tube is a rare condition in which the pharyngotympanic tube is intermittently open, creating echoes of internal sounds that are disruptive to a person's hearing and speech.

To correct some of these problems, several interventions can be carried out. In severe cases where the infection reaches the inner ear and there is permanent blockage of the pharyngotympanic tubes, a ventilation and drainage pathway can be provided by surgical puncture of the tympanic membrane; this operation is known as myringotomy and is usually performed mainly in children. The hole in the eardrum tends to heal on its own, so sometimes a small tube is inserted to keep it open (tympanostomy tube).

As an alternative to myringotomy and depending on the case, they can be implanted prosthesis inside the pharyngotympanic tubes that allow them to open properly. They are usually implants that facilitate ventilation but do not necessarily keep the tube open permanently. However, these prostheses can promote the production and accumulation of mucus and require frequent cleaning.

In case of eustachian tube hypertrophy, the ventilation problem comes from an excess of fabric. In these cases, an intervention known as microdebridement either tuboplasty to remove tissue and facilitate ventilation.

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