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Gastrointestinal function secretion, regulation

Gastrointestinal function secretion, regulation. Daniel Hodyc Department of Physiology. Pictures and schemes – L. R. Johnson – Essential Medical Physiology, Elsevier, 2003. GIT secretion. 1. Salivary secretion 2. Gastric secretion 3. Pancreatic secretion. Salivary secretion.

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Gastrointestinal function secretion, regulation

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  1. Gastrointestinal function secretion, regulation Daniel Hodyc Department of Physiology Pictures and schemes – L. R. Johnson – Essential Medical Physiology, Elsevier, 2003

  2. GIT secretion 1. Salivary secretion2. Gastric secretion3. Pancreatic secretion

  3. Salivary secretion

  4. Anatomy, Inervation

  5. Functions of saliva Digestion - ptyalin (α-amylase) - identical to pancreatic amylase - cleaves α-1,4-glycosidic bonds of carbohydrates - 75 % of starch, pH optimum 7 - functionally replaceable by pancreatic enzyme - lingual lipase - triglycerides - lower acidic optimum – remains active throughout the stomach and into the proximal duodenum - dissolves dietary constituents - increases the sensitivity of taste buds

  6. Functions of saliva Lubrication - mucus content - facilitates swallowing - necessary for speech Protection -dilution and buffering of harmful substances - salivation before vomiting - xerostomia chronic infections - lysozym, IgA binding protein, lactoferin - take-up of Ca and phosphate - concentration

  7. Composition of saliva Major characteristics of saliva: - relatively large volume - high potassium concentration - low osmolarity - two stages in secretion acini x salivary duct - specialized organic materials

  8. Composition of saliva

  9. Composition of saliva

  10. Composition of saliva Organic composition: - ptyalin, lipase - lysozym, IgA binding protein, lactoferin kallikrein α-globulin bradykinin vasodilation

  11. Neural regulation of secretion

  12. Gastric secretion

  13. Gastric secretion Gastric juice - hydrochloric acid - conversion of pepsinogen to pepsine - bacteriostatic effect - pepsin - protein digestion - replaceable by pancreatic enzymes - mucus - protective coating, lubricant - part of gastric mucosal barrier - intrinsic factor - binds B12 vitamin, absorption in the ileum - the only indispensable substance in gastric juice

  14. Gastric secretion Oxyntic gland Secretory regions

  15. Gastric juice electrolytes

  16. Hydrochloric acid secretion alkaline tide

  17. Stimulation of acid secretion Potentiation of agents Parasympathetics (Ach) Gastrin Histamine

  18. Hydrochloric acid secretion – perietal cell Nonsecreting cell Secreting cell

  19. Stimulation of acid secretion – cephalic phase blocked by vagotomy sham feeding hypoglycemia role of GRP (bombesin)

  20. Gastric phase 60 % of acid response distension peptides calcium alcohol caffeine

  21. Stimulation of gastric acid secretion

  22. Regulation of gastrin release Acetylcholine - Somatostatin Cell Gastrin Cell

  23. Intragastric pH after a meal Stomach – somatostatin Duodenum – secretin, hyperosmotic chyme fatty acids Inhibition of acid secretion

  24. Production of Pepsin Pepsinogen Ach H+ Pepsin

  25. Pancreatic secretion

  26. Secretion of water and electrolytes Na, K – the same as in plasma Bicarbonate concentration – up to 5 times higher than in plasma

  27. Mechanism of water and electrolytes secretion Na-K-ATPase Bicarbonate in plasma High extracellular Cl- concentration Carbonic anhydrase

  28. Mechanism of enzymes secretion Proteolytic enzymes – secreted as inactive precursors chymotrypsinogen prokarboxypeptidase enterokinase trypsinogen trypsin chymotrypsin karboxypeptidase

  29. Mechanism of enzymes secretion Inhibition of pancreatic autodigestion chymotrypsinogen prokarboxypeptidase enterokinase trypsinogen trypsin Trypsin inhibitor chymotrypsin karboxypeptidase

  30. Mechanism of enzymes secretion Inhibition of pancreatic autodigestion chymotrypsinogen prokarboxypeptidase enterokinase trypsinogen trypsin Trypsin inhibitor chymotrypsin karboxypeptidase Failure PANCREATITIS

  31. Mechanism of enzymes secretion Glycolytic enzymes - secreted as active enzymes - pancreatic α-amylase - cleaves starch and glycogen into di- and trisacharides Lypolytic enzymes - secreted as active enzymes - pancreatic lipase - glycerol + fatty acids

  32. Regulation of pancreatic secretion Cephalic and gastric phase Acetylcholine CCK enzymes Secretin water bicarbonate

  33. Regulation of pancreatic secretion Intestinal phase Acetylcholine CCK Fat enzymes H+ Secretin water bicarbonate

  34. Response to a meal neutralization - pancreatic bicarbonate changes in diet changes in enzyme secretion

  35. The effect of potentiation of enzyme secretion in pancreas Phenylalanin + Secretin (CCK) Secretin 1unit / kg.hr Phenylalanin (CCK)

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