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Digestive System

Digestive System. Pancreas – Large Intestine. Pancreas (accessory). Location Pancreatic duct Islets. Pancreas. Pancreatic Juice Acinar Cells – exocrine Bicarbonate Pancreatic Amylase. Pancreas. Protein Enzymes Trypsin Chymotrypsin Carboxypolypeptidase Lipase.

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Digestive System

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  1. Digestive System Pancreas – Large Intestine

  2. Pancreas (accessory) • Location • Pancreatic duct • Islets

  3. Pancreas • Pancreatic Juice • Acinar Cells – exocrine • Bicarbonate • Pancreatic Amylase

  4. Pancreas • Protein Enzymes • Trypsin • Chymotrypsin • Carboxypolypeptidase • Lipase

  5. Controls of Juice Release • Secretin • Cholecystokinin • Neurally – Vagus nerve stimulates release

  6. Liver (accessory) • Hepato- • 4 lobes; Falciform ligament separates large R & L lobes • Cells are hepatocytes • Common Bile Duct (Hepatic duct + Gall bladder duct), which empties into duodenum

  7. Liver • Blood supply – enormous • Bile Production • 600-1000 mls per day • Liver cells make bile, gall bladder STORES bile

  8. Bile Composition • Water • Bilirubin (from Hb breakdown) • Bile Salts function in Emulsification

  9. Enterohepatic Circulation • Bile salts secreted into duodenum, are reabsorbed in ileum and returned to liver

  10. Bile Secretion Controls • Enterohepatic Circulation • Vagus Nerve • Secretin • Increased hepatic blood flow • Cholecystokinin

  11. More liver functions • Metabolic regulation (blood filtering, monitoring blood) • Clotting factors are made by liver • Blood protein synthesis • Phagocytosis of old WBC & RBCs • Detoxification, storage of toxins • Stores glucose (glycogen), fat, protein, Cu, Fe, Vitamins

  12. SUMMARY of GI HORMONES • GASTRIN • Made by pylorus cells • Increases gastric motility • Increases gastric secretions

  13. SUMMARY of GI HORMONES • SECRETIN • Made by duodenal cells • Decreases gastric motility & secretions • Increases pancreatic juice release • Increases bile secretion

  14. SUMMARY of GI HORMONES • CHOLECYSTOKININ • Made by duodenal cells • Decreases gastric motility & secretions • Increases pancreatic juice release • Increases gall bladder contraction

  15. SUMMARY of GI HORMONES • GIP (Gastric Inhibitory Peptide) • Made by duodenal cells • Decreases gastric motility & secretions • Promotes insulin release

  16. Small Intestine • 21 foot tube • Duodenum – 1 foot • Jejunum – 8 ft. • Ileum – 12 ft.

  17. Small Intestine Microstructure • Villi • Microvilli • Blood vessels • Lacteals

  18. Small Intestinal Secretions • 2-3 liters of “juice” per day • Duodenal glands (Brunner’s) make protective mucus • Intestinal glands make isotonic fluid containing some digestive enzymes

  19. Small Intestine Motility • Segmentation • Peristalsis

  20. Absorption • Definition – 90% of all absorption occurs in SI • Nutrients from SI to blood or lymph vessel • Villi & Microvilli • Processes include active transport, diffusion, facilitated diffusion, cotransport

  21. Absorption • Carbohydrates • Proteins • Lipids • Emulsification • Lipase • Micelles (fat + bile salt) • Chylomicrons • Lacteals

  22. Absorption • Vitamins (ADEK along with fat, B’s and C along with water)

  23. Absorption • Water & Electrolytes (ions in soln.) • 9 liters/day by osmosis • Sodium • Calcium absorption is Vit. D dependent

  24. Large Intestine • Five feet long • Cecum • Ileocecal sphincter = valve • Appendix

  25. Large Intestine • Colon • Ascending • Transverse • Descending • Sigmoid • Rectum • Anus

  26. Large Intestine • No villi • Goblet cells make mucus • Taeniae coli – flat muscular bands • Haustra – pouches as taeniae coli contract

  27. Large Intestine Motility • Peristalsis • Haustral churning • Mass peristalsis drives contents into rectum • Gastroileal reflex activates mass peristalsis • Defecation reflex • Anal sphincters – Internal and External

  28. Large Intestine Functions • Some water absorption • Lubrication of contents • Form and store feces • Synthesis of Vitamin K and some B vitamins and absorption • Bacterial fermentation

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