Stomach and Intestinal Action. Gastric juice in the stomach contains agents such as hydrochloric acid and some enzymes, including pepsin, rennin, and lipase. Pepsin breaks proteins into peptones and proteoses. Another function of stomach digestion is gradually to release materials into the upper small intestine, where digestion is completed. These fluids neutralise the gastric acid, ending the gastric phase of digestion.
Pancreatic fluid is introduced into the small intestine through several ducts .
It contains trypsin and chymotrypsin, enzymes that split complex proteins into simpler components that can be absorbed and used in reconstructing body proteins. Other enzymes then break these into glucose and fructose . Secretion of pancreatic juice is stimulated by the ingestion of proteins and fats. I ntestinal juice is secreted by the small intestine. The flow of intestinal juice is stimulated by the mechanical pressure of food partly digested in the intestine.