chyme, 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 (peristalsis) moves the chyme into the duodenum, the first section of the small intestine, where 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.

Thick semifluid mass of partly digested food and secretions, formed in the stomach and intestines during digestion. Its composition changes as various digestive juices and cellular debris and other waste products are added, and water and nutrients are absorbed from it during its passage through the digestive tract, at the end of which it is stored for excretion.

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