What happens to the upper esophageal sphincter during the swallowing process?

During the swallowing process, the upper esophageal sphincter relaxes. This sphincter serves as a barrier between the pharynx and the esophagus, coordinating its movement with the act of swallowing. When a person swallows, a series of neurological signals trigger the sphincter to open, which allows the bolus (a mass of food or liquid) to enter the esophagus from the pharynx. This relaxation is crucial for the proper passage of food and liquids down into the esophagus without obstruction.

If the upper esophageal sphincter were to contract instead of relax, it would impede the bolus from passing through and could lead to choking or discomfort. Furthermore, while it does close to prevent air from entering the esophagus during breathing, its primary action during swallowing is to open, facilitating the safe transition of substances from the throat to the esophagus.