Swallowing consists of 3 phases that follow one another to complete the other.
The first phase is voluntary and begins with the selective separation of the chewed food until it forms a mass or bolus. This separation is mainly produced by the language. The bolus is placed on the back of the tongue and pressed lightly against the hard palate. The tip of the tongue rests on the hard palate just behind the incisors. The lips are sealed and the teeth are together. The presence of the bolus on the mucosa of the palate initiates a reflex wave of contraction in the tongue that pushes it back. When this reaches the back of the tongue, it is transferred to the pharynx.
Once the bolus has reached the pharynx the second phase begins, a peristaltic wave caused by the contraction of the constrictor muscles of the pharynx takes it to the esophagus. The soft palate rises to touch the posterior pharyngeal wall, closing the nasal passages. The epiglottis blocks the pharyngeal airway to the trachea and keeps food in the esophagus. During this phase of swallowing, pharyngeal muscle activity opens the pharyngeal orifices of the auditory tubes, which are normally closed. These first two phases of swallowing together are estimated to last approximately 1 second. It should be noted how important it is for correct tubal function during swallowing.
The third phase of swallowing involves passing the bolus through the esophagus and into the stomach. Peristaltic waves take 6 to 7s to transport the bolus through the esophagus.
When the bolus approaches the cardiac sphincter (of the cardia), the sphincter relaxes and allows it to enter the stomach. In the upper section of the esophagus, the muscles are primarily voluntary and can be used to return food to the mouth when necessary for more complete chewing. In the lower section, the muscles are completely involuntary.
The literature says that the swallowing cycle occurs approximately 590 times during a 24-hour period: 146 cycles during meals, 394 cycles between meals while awake, and 50 cycles during sleep. Low levels of salivary flow during sleep lead to less need to swallow.
Valentina Carlile - Osteopath expert in Osteopathy applied to voice and speech disorders since 2002. For information and reservations visit the page Contacts