Topics: Gastrointestinal Physiology, Gastrointestinal system, mucosa, serosa, Deglutition, Gastrin secretion, Peristaltic Rush, Ileocecal Valve, small intestine, Defecation Reflexes, defecation, Gastrointestinal secretions, salivary secretion, Salivary Glands, saliva, esophageal secretion gastric secretion, Gastric Juice Secretions, pancreatic secretions, Pancreatic Juice, Pancreatic Digestive Enzymes, biliary secretions, large intestine, digestion, absorption, Glucose Absorption, Galactose Absorption, Fructose Absorption, carbohydrate digestion, protein digestion, lipid digestion