The opening of the gastroesophageal sphincter, also known as the lower esophageal sphincter (LES), is primarily triggered by peristalsis in the esophagus.
When food is swallowed, it travels down the esophagus through a series of coordinated muscle contractions called peristalsis. As the food bolus approaches the end of the esophagus, it exerts pressure against the LES. This pressure is what signals the sphincter to relax and open, allowing the food to enter the stomach.
This process is crucial for ensuring that food moves smoothly from the esophagus into the stomach, while also preventing the backflow of stomach contents, which can lead to conditions like gastroesophageal reflux disease (GERD).