Is there a valvular structure between stomach and duodenum? If yes, what is it and what is the role?
The Pyloric Sphincter is a band of smooth muscle at the base of the stomach forming the junction between the stomach pylorus (the lower part of the stomach) and the duodenum.
Food which enters the stomach is mixed with gastric acid to form a tick acidic liquid called chyme, during which time the pyloric sphincter is closed. After the digestion in the stomach is complete, waves of peristalsis move the chyme towards the pylorus and the pyloric sphincter opens with each peristaltic wave to allow a small mass of the chyme to pass through it into the duodenum for the next stage of digestion and absorption of nutrients.
While the pyloric sphincter controls the passage of chyme into the duodenum, it also prevents regurgitation of the chyme into the stomach,