Regulation of Digestion The activities of the digestive system are regulated by both hormones and neural reflexes. Four important hormones and their effects on target cells follow: Gastrin is produced by enteroendocrine cells of the stomach mucosa. Effects include: • Stimulation of gastric juice (especially HCl) secretion by gastric glands. • Stimulation of smooth muscle contraction in the stomach, small intestine, and large intestine, which increases gastric and intestinal motility. • Relaxation of the pyloric sphincter, which promotes gastric emptying into the small intestine. • Secretin is produced by the enteroendocrine cells of the duodenal mucosa. Effects include: • Stimulation of bicarbonate secretion by the pancreas, which stabilizes the pH of the chyme when released into the duodenum. • Stimulation of bile production by the liver.
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