GI Physiology Study Guide The Story of One Meal (PGY 300 Exam 4)

Let's explore GI physiology, focusing on how a meal travels through our bodies. We'll cover digestion, absorption, and the body's control mechanisms.Our journey starts from the mouth, through the esophagus, stomach, small intestine, large intestine, and finally to the anus. Accessory organs like the liver and pancreas are also key.In the large intestine, we have rugae and plicae, but no villi. The epithelium's cell types, like enterocytes and goblet cells, play vital roles in absorption and protection.The microbiome, with trillions of cells, helps digestion and nutrient absorption. Our gut also has its own engine for movement, driven by interstitial cells of Cajal.Gut motility involves peristalsis, segmentation, and mass movements. Swallowing is a complex process, involving both voluntary and involuntary actions.Our digestive system is controlled by reflexes and hormones. The "brain of the gut," the ENS, plays a crucial role in regulating these processes.Hormones like Gastrin and Secretin regulate stomach acid and pancreatic secretions. A classic example is motilin, which triggers the migrating motor complex.Salivary glands produce mucus and amylase, while the stomach creates HCl and pepsin. The pancreas and liver also contribute vital enzymes and bile.Digestion and absorption primarily happen in the small intestine. Carbohydrates break down into monosaccharides, and fats are emulsified and absorbed.Vitamins and minerals, like Vitamin B12, Iron, and Calcium, have specific absorption pathways in the gut. Water is mostly reabsorbed in the small intestine.