The pyloric sphincter, or valve, is a strong ring of smooth muscle at the end of the pyloric canal and lets food pass from the stomach to the duodenum. It receives sympathetic innervation from celiac ganglion. http://en.wikipedia.org/wiki/Pylorus

The pyloric sphincter regulates passage of chymefrom the stomach

The ring like muscle that controls the flow from the stomach to the small intestine is called the pylorus or the pyloric sphincter. It is divided into two parts: the pyloric antrum which is connected to the body of the stomach and the pyloric canal which is connected to the beginning of the small intestine (the duodenum).

Pyloric sphincter controls the movement of food from stomach to duodenum. With parasympathetic or vagal stimulation it opens up or relaxes and with sympathetic stimulation it contracts or closes.