Chyme

Chyme is the semifluid mixture of partially digested food and digestive secretions that forms in the stomach during digestion. After swallowed food, called a food bolus, enters the stomach, it is mixed and mechanically broken down by muscular contractions while being exposed to gastric secretions. This processing transforms the more cohesive food bolus into chyme .^1,2

Chyme contains food particles mixed with water and substances secreted into the stomach, including hydrochloric acid and digestive enzymes. The acidic environment helps denature proteins and promotes the conversion of pepsinogen to pepsin, an enzyme involved in protein digestion. At the same time, repeated stomach contractions grind and mix the contents, breaking solid food into smaller particles .¹

Chyme is gradually released through the pyloric sphincter into the duodenum, the first part of the small intestine. There, its acidity is reduced by bicarbonate, and it mixes with pancreatic secretions and bile as digestion continues. Chyme therefore describes digestive contents at a particular stage of processing rather than a specific substance produced by one organ. It differs from a food bolus, which is the mass of chewed food and saliva formed before and during swallowing .^1,2