Actions of the digestive system

Fig. 15-2, Vander’s Human Physiology, 11th edition (2008)

• secretion • digestion • absorption • motility Internal vs. external environment Overview of digestive tract function

Figure 21.6, p. 667 Components of the digestive system

GI TRACT ACCESSORY GLANDS mouth and pharynx salivary glands esophagus stomach small intestine duodenum jejunum liver ileum gallbladder pancreas large intestine rectum

Figure 21.1a, p. 656 Structure of the stomach

Figure 21.1c, p. 656 Structure of the small intestine

Figure 21.1d, p. 656 Digestive secretions entering the duodenum

pancreas: • digestive enzymes • bicarbonate liver: • bile salts (solubilize fats) • bicarbonate (gallbladder stores bile) Duodenal papilla: outlet for pancreatic duct and common bile duct

Figure 4.109, Gray’s Anatomy for Students Anatomy of the bile ducts

cystic bile duct hepatic bile duct common bile duct

Adapted from Figure 4.111, Gray’s Anatomy for Students Anatomy of the large intestine

From Figure 21.21, p. 686 Structures to identify on the large model of the digestive tract:

hard palate common bile duct soft palate small intestine tongue duodenum salivary glands duodenal papilla epiglottis jejunum/ileum esophagus large intestine stomach cecum greater curvature ileocecal valve lesser curvature appendix fundus ascending colon body transverse colon antrum (pylorus) descending colon pyloric sphincter (pyloric valve) sigmoid colon pancreas rectum pancreatic duct anal canal liver external anal sphincter Blood flow to the liver Structures to identify on the model of the liver with gallbladder and duodenum

duodenum jejunum gallbladder bile ducts hepatic bile duct cystic bile duct common bile duct pancreas pancreatic duct hepatic portal vein common hepatic artery Structures to identify on the model of the pancreas with spleen and part of the duodenum

duodenum plicae circulares duodenal papilla jejunum pancreas pancreatic duct common bile duct hepatic portal vein common hepatic artery Clinical example: bariatric surgery

bariatric surgery à weight loss surgery two most common procedures • sleeve gastrectomy • Roux-en-Y gastric bypass treatment for type 2 diabetes mellitus: remission rates following surgery Sleeve gastrectomy

“restrictive”—smaller stomach reduces food intake ↓ ghrelin secretion ghrelinàhormone secreted by stomach cells that increases appetite Roux-en-Y gastric bypass (RYGB) Configuration of GI tract after RYGB Endocrine changes after RYGB

àreduction or removal of stomach decreases ghrelin secretion

àbypass of stomach and upper intestine changes secretion of an unknown hormone àfaster delivery of chyme to distal small intestine increases secretion of GLP-1 and PYY GLP-1 is an incretin

• secreted by endocrine cells in small intestine epithelium • secretion stimulated by glucose, fats in small intestine • increase glucose-dependent insulin secretion • incretin-based drugs used in the treatment of type 2 diabetes mellitus • GLP-1 also has effects on CNS control of appetite Secretion and Action of Incretins

incretins: GIP, GLP-1

*look for a web page about bariatric surgery by next week