Final answer:
When food enters the esophagus, peristalsis propels it towards the stomach. The lower esophageal sphincter controls the flow of food into the stomach.
Step-by-step explanation:
The esophagus is a narrow tube that carries food from the throat to the stomach. When food enters the esophagus, peristalsis, which is the rhythmic contraction and relaxation of muscles, propels the food towards the stomach. At the lower end of the esophagus, there is a circular muscle called the lower esophageal sphincter, which controls the opening to the stomach. This muscle relaxes to allow food to pass into the stomach and then contracts again to prevent food from flowing back into the esophagus.