Gastrin, secretin, and cholecystokinin are hormones that regulate stages of digestion. Protein in the stomach stimulates secretion of gastrin, which causes increased stomach acid secretion and mobility of the digestive tract to move food. Food passing into the duodenum causes the production of secretin, which in turn promotes release of alkaline secretions from the pancreas, stops further passage of food into the intestine until the acid is neutralized. Cholecystokinin (CCK) is released from intestinal epithelium in response to fats, and causes the release of bile from the gall bladder and lipase (a fat digesting enzyme) from the pancreas.

Glucose Metabolism

Glucose levels in the blood remain fairly stable. The liver absorbs glucose from the blood and stores it as the polysaccharide glycogen. Blood glucose levels are maintained between meals by releasing glucose from glycogen back into the blood.

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