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
1. Salivary secretion 2. Gastric secretion 3. 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 Protection
- 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 acid response alcohol caffeine  60 % of  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
- 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 - pancreatic bicarbonate changes in diet changes in
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)