The pylorus is the structure that connects the stomach to the duodenum -- it consists of two parts. The first is the pyloric antrum, which is the opening to the stomach itself, while the other is the opening to the duodenum, the pyloric canal. At the end of the canal is the pyloric orifice. The pyloric sphincter surrounds this orifice and acts as a gateway. When the sphincter relaxes, partially digested food -- chyme -- travels from the stomach into the duodenum.

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