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

2. 1. Salivary secretion 2. Gastric secretion 3. Pancreatic secretion GIT 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

10. Organic composition: - ptyalin, lipase - lysozym, IgA binding protein, lactoferin α-globulin bradykinin kallikrein 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 B 12 vitamin, absorption in the ileum - the only indispensable substance in gastric juice

14. Gastric secretion Secretory regions Oxyntic gland

15. Gastric juice electrolytes

16. Hydrochloric acid secretion alkaline tide

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

18. Hydrochloric acid secretion – perietal cell Nonsecreting cellSecreting 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 Gastrin Cell Somatostatin Cell Acetylcholine -

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

24. Production of Pepsin Ach H+ H+ Pepsinogen 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 trypsinogen trypsin enterokinase chymotrypsinogen prokarboxypeptidase chymotrypsin karboxypeptidase

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

30. Mechanism of enzymes secretion Inhibition of pancreatic autodigestion trypsinogen trypsin enterokinase chymotrypsinogen prokarboxypeptidase chymotrypsin karboxypeptidase Trypsin inhibitor 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 Secretin water bicarbonate enzymes

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

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)

36. Regulation of secretion - autonomic nervous system control - in contrast to other glands (gastric, pancreatic) - Aldosterone and ADH modulate ionis content, not the flow