The pyloric sphincter is a band of smooth muscle at the junction between the pylorus of the stomach and the duodenum of the small intestine. It plays an important role in digestion, where it acts as a valve to controls the flow of partially digested food from the stomach to the small intestine. The constriction of sphincter prevents the foods to empty into intestine until foods are mixed well with gastric juice (containing HCl and enzymes). Pyloric sphincter also prevents backflow of chyme from intestine (duodenum) to stomach. When the pyloric sphincter doesn’t work properly, bile can make its way up the digestive tract.