Lateral oblique view of a male torso featuring digestive organs. The digestive system is comprised of an alimentary canal and accessory organs; together they break down complex food into simple structures the body can use, absorb the nutrients into the blood stream, and eliminate waste. Food passes from the esophagus to the stomach through the cardiac sphincter, which prevents chyme, the thick semifluid mass of partly digested food, from returning to the esophagus. After chemical and mechanical digestion in the stomach, the chyme moves to the first part of the small intestine (the duodenum) through the pyloric sphincter, which controls the rate of stomach emptying.