Chyme

Gastric chyme is the semiliquid substance found in the stomach and resulting from the partial digestion of food by the salivary enzyme amylase, the gastric enzyme pepsin, and hydrochloric acid. Secretion of hydrochloric acid by the stomach makes the chyme strongly acidic. The rhythmic muscular action of the stomach wall releases the chyme into the duodenum through the pyloric valve. In the duodenum (small intestine) it stimulates the release of secretin, a hormone that increases the flow of pancreatic juice as well as bile and intestinal juices. Chyme also stimulates the release of cholecystokinin, a hormone that primarily increases the flow of bile but also increases the proportion of digestive enzymes in the pancreatic juice.

Chyme has a pH of around 2 and emerged from the stomach very acidic. To raise its pH, the duodenum secretes cholecystokinin (CCK), which causes the gall bladder to contract, releasing alkaline bile into the duodenum.