10/4/2023 0 Comments Nasopharynx auditory tubeThe diagnosis of Eustachian tube dysfunction is poorly defined, with no existing comprehensive guidelines. This process is enhanced as the tube matures and becomes more oblique in angle, allowing gravity to play a role in the drainage process. Īlso of importance in the proper function of the Eustachian tube is the mucociliary clearance of middle ear secretions to the nasopharynx. It is these surfactants that aid in reducing the surface tension of the ET lumen and thus reduce the work required to dilate the tube. Of note, tubal dilation is facilitated by the presence of surfactants, surface tension-reducing substances found in the mucus of the ET. Intermittent brief tubal dilation of the ET occurs multiple times per day, occurring approximately 1.4 times/minute and remaining open for approximately 0.4 seconds. Two additional muscles associated with the Eustachian tube that have not been shown to play a significant role in the opening of the lumen include the tensor tympani and salpingopharyngeus muscles. This mechanism also clarifies why exaggerated Eustachian tube dysfunction will result in hearing deficits if a gas exchange deficit occurs in the middle ear, causing the tympanic membrane to tauten. This explains why dilation of the Eustachian tube allows air at atmospheric pressure to equilibrate with the lower partial pressures of gas in the middle ear that develop. Carbon dioxide and oxygen readily pass through the venous capillary membranes, creating a net pressure vacuum in relation to atmospheric pressure. The pressure discrepancy between the middle ear and the atmosphere is due to the diffusion of atmospheric gases across venous capillary cell membranes in the middle ear. Simultaneous contractions of these muscles during swallowing or yawning allow air to pass through the ET to equilibrate pressure in the middle ear with the atmosphere. Contraction of the levator veli palatini results in elevation of the soft palate and medial rotation of the cartilaginous lamina. The tensor veli palatini contracts the anterolateral wall to cause dilation and opening of the distal Eustachian tube. While the Eustachian tube is closed at rest, it relies on its interaction with two muscles to help facilitate its opening the tensor veli palatini and the levator veli palatini.
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