Final answer:
Food moves through the digestive tract through peristalsis, which is the sequential contraction and relaxation of the smooth muscles in the canal walls. This movement propels food in the proper direction and prevents it from going the wrong direction.
Step-by-step explanation:
Food moves through the digestive tract through a process called peristalsis, which is the sequential contraction and relaxation of the smooth muscles in the walls of the alimentary canal. This movement propels food in the proper direction and prevents it from going the wrong direction. Peristalsis is responsible for moving food from the mouth to the esophagus, and from the stomach to the small intestine and eventually to the anus. The powerful waves of peristalsis are so effective that food can still travel through the esophagus even when a person is upside down.