Physiology: The digestive system

... epithelium www.cambodiamed.com Regulation of the GI Tract • Extrinsic innervation: • Parasympathetic nervous system: • Vagus and spinal nerves: • Stimulate motility and GI secretions • Sympathetic... elastase, and histamine are secreted into the lumen of the GI tract • Endocrine: • Stomach and small intestine secrete hormones to help regulate the GI system • Gastrin, secretin, CCK, GIP, GLP-1,... through the GI tract • Inner circular layer of smooth muscle • Outer longitudinal layer of smooth muscle • Contractions of these layers move food through the tract; pulverize and mix the food