impaired swallowing
swallowing
[swahl´o-ing]Normally, air is free to pass from the nose or mouth to the lungs and back again. But the moment the bolus approaches the fauces, the passage from the mouth to the pharynx, nerve centers are triggered that control a series of reflex actions. After one quick inhalation, breathing is halted for the brief instant of the next stage.
In this second, involuntary, stage of swallowing, the rear edge of the soft palate, which hangs down from the roof of the mouth, swings up against the back of the pharynx and blocks the passages to the nose. The back of the tongue fits tightly into the space between two muscular pillars at each side of the fauces, sealing the way back to the mouth. Simultaneously, the larynx moves upward against the epiglottis, effectively closing the entrance to the trachea.
Sometimes the larynx does not move up quickly enough and food gets into the air passage, stimulating a coughing reaction. With the one-way route to the stomach firmly established, however, the muscular coat of the pharynx contracts, squeezing the ball of food and forcing its passage into the esophagus.
In the third stage, the rhythmic contraction (peristalsis) of the muscles of the esophagus moves the food on to the stomach. The cardiac sphincter keeps the stomach entrance closed until food is swallowed. As the food approaches, moved by the wavelike contractions of the esophagus, the advancing portion of the wave causes the sphincter to relax and open, while the rear and contracting portion forces the ball of food through the entrance.