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Announcements Tomorrow’s quiz on NEJM paper Bring two questions about NEJM Exam I provided today Which of the following enzymes work most effectively at a very low pH? A. Salivary amylase B. Trypsin C. Pepsin D. Pancreatic amylase E. Pancreatic lipase In zero gravity environment of space, how does food swallowed by an astronaut reach her stomach? A. Swallowing hard B. Running around wheel creates -> artificial gravity C. Involuntary muscle contractions D. IV administration of nutrients Which of the following organs is incorrectly paired with its function? A. Stomach –protein digestion B. Oral cavity -starch digestion C. Large intestine –bile production D. Small intestine –nutrient absorption E. Pancreas –enzyme production Salivary glands Secretes enzymes that digest carbohydrates 1. Mouth Mechanical and chemical processing (chewing reduces size of food; saliva digests carbohydrates) Liver Secretes molecules required for digestion of fats 2. Esophagus Transports food Gall bladder Stores secretions from liver; empties into small intestine 4. Small intestine Chemical processing and absorption (digestion of proteins, fats, carbohydrates; absorption of nutrients and water) Pancreas Secretes enzymes and other materials into small intestine 3. Stomach Mechanical and chemical processing (digestion of proteins) 5. Large intestine Water absorption and feces formation Stomach End of esophagus Sphincter seals off stomach from esophagus Sphincter seals off stomach from small intestine Layers of muscle Beginning of small intestine Lumen (interior) Stomach lining Canal empties to lumen Parietal cells (secrete HCl) Chief cells (secrete pepsinogen) Secretion of HCI by parietal cells HCl to lumen CO2 + H 2O H2CO3 To blood H+ H+ HCO3– Cl– HCO3– K+ H+/K+ pump Cl– Cl– Cl– Chloride channel From blood Parietal cell Canal empties to lumen Enzymes, Hormones, other? •Enzymes: pepsinogen (inactive)-> pepsin (protease) from chief cells •Other: HCl -> denature ECM bacteria, from parietal cells, activator of pepsin •Other: Mucins/mucus protective from goblet or mucus cells •Other: mechanical churning -> acid chyme •Hormones: Gastrin (+), CCK/secretin (-), enterogastrone (-- pyloric sphinct) Enzymes, Hormones, other? •Your turn DIGESTION OF LIPIDS IN SMALL INTESTINE Glycerol Lipase Fatty acids 1. Large fat globules are not digested efficiently by lipase. 2. Bile salts (produced in liver) act as emulsifying agents. 3. Small fat droplets result from emulsification. 4. Lipase digests the small fat droplets into glycerol and free fatty acids. Fold Villi 115 µm Cross-section of small intestine Lumen of small intestine Apical side Na+/glucose cotransporter H2O Osmosis Na+ Glucose K+ GLUT-2 transport protein Na+/K+-ATPase K+ ATP Basolateral side ADP Blood H2O Osmosis Na+ Glucose Capillaries are small and extremely thin walled. Glucose Pancreas secretes INSULIN If glucose levels too high If glucose levels too low Pancreas secretes GLUCAGON Glycogen Insulin causes cells in the liver and skeletal muscle to synthesize glycogen; fat storage cells synthesize triglycerides. Glucose levels fall HOMEOTASIS (normal glucose levels in blood) Glucose levels rise Glucagon causes cells in liver and skeletal muscle to catabolize glycogen; fat storage cells catabolize fatty acids. Glycogen Glucose