1. Gastric Secretion
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gastric secretion

2. Gastric Secretion Gastric juice HCl Electrolytes Mucus, Water
Intrinsic factor
Bicarbonate
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gastric secretion

3. Gastric Gland Gastric (oxyntic) gland cell types
Gastric lumen
Gastric (oxyntic) gland cell types
Surface epithelia cells (mucus cells)
Alkaline mucus- viscid
Mucous neck cells (neck chief cells)
Soluble mucus
pepsinogen
Columnar mucus cells
Mucous neck cell
Parietal cell
Peptic cell
From Physiology Book by H.T. Sherrief
31-Jul-19
gastric secretion

4. Gastric Gland Parietal cell Produce a solution containing
Gastric lumen
Parietal cell
Produce a solution containing
Approx. 160 mmol of HCl/l; pH 0.8 (H+ conc. = 3 to 4 million time that in plasma)
Energy cost = 1500 calories/l of HCl
Intrinsic factor (vit. B12 - R factor binding macromolecule)
Columnar mucus cells
Mucous neck cell
Parietal cell
Peptic cell
From Physiology Book by H.T. Sherrief
31-Jul-19
gastric secretion

5. Gastric Gland Parietal cell also produce Gastric lipase
Gastric lumen
Parietal cell also produce
Gastric lipase
Gastric amylase
Gelatinase
Columnar mucus cells
Mucous neck cell
Parietal cell
Peptic cell
From Physiology Book by H.T. Sherrief
31-Jul-19
gastric secretion

6. Gastric Gland Chief [peptic] cells (zymogen cells) produce Pepsinogen
Gastric lumen
Chief [peptic] cells (zymogen cells) produce
Pepsinogen
Contain Pepsinogen( PG I, PG II)
Small volume of electrolyte similar to ECF
Some individuals secrete ABO blood group antigen in their gastric juice
Columnar mucus cells
Mucous neck cell
Parietal cell
Peptic cell
From Physiology Book by H.T. Sherrief
31-Jul-19
gastric secretion

7. Gastric Gland Enterochromaffin cells Specialized cells serotonin
Gastric lumen
Enterochromaffin cells
serotonin
Histamine
Specialized cells
Vasoactive intestinal peptide (VIP)
Substance P
Glucagon
Columnar mucus cells
Mucous neck cell
Parietal cell
Peptic cell
From Physiology Book by H.T. Sherrief
31-Jul-19
gastric secretion

8. Pyloric Gland Similar structure like the oxtntic gland Have G-cells
Gastric lumen
Similar structure like the oxtntic gland
Contain few peptic (chief) cells
No parietal cells
Contain mucus cells
Have G-cells
Columnar mucus cells
Mucous neck cell
G-cells
Peptic cell
From Physiology Book by H.T. Sherrief
31-Jul-19
gastric secretion

9. Pyloric Gland secrete G cells produce Gastrin
Gastric lumen
secrete
Mucus and electrolytes
G cells produce Gastrin
Peptic cells produce pepsinogen
Columnar mucus cells
Mucous neck cell
G-cells
Peptic cell
From Physiology Book by H.T. Sherrief
31-Jul-19
gastric secretion

10. HCL Secretion Function of HCL
Participates in the breakdown of proteins
Provide optimal pH for pepsin
Hinders growth of pathogenic bacteria
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gastric secretion

11. Mechanisms of HCL Secretion
Chloride ions are actively secreted into lumen of canaliculi
Against concentration gradient
creates a negative potential -40 to -70 mv in canaliculi
passive diffusion of K+, Na+
KCl, NaCl
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gastric secretion

12. Mechanism of Acid Secretion
The H+ conc. In parietal cells
3 to 4 million fold higher than in blood
Cl- is secreted against
Concentration and electrical gradient
Ability of parietal cell to secrete acid
Dependent on active transport
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gastric secretion

13. Mechanism of Acid Secretion
Key player in acid secretion
H+/K+ATPase or “proton pump”
Mg++ dependent
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gastric secretion

14. Mechanisms of Acid Secretion
Dissociation of H2O
H2O  H+ + OH -
The H+ is then actively secreted into the lumen by active pump in exchange of K+
Proton pump
H+/K+ ATPase
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gastric secretion

15. Mechanism of Acid Secretion
Na+ is actively reabsorbed by a separate pump
Thus most of the Na+, K+ that had diffused into canaliculi
Reabsorbed into the cell
H+ take their place
Giving strong solution of HCL
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gastric secretion

16. Mechanism of Acid Secretion
The OH - combine with CO2 to form HCO3-
Carbonic Anhydrase
The HCO3 - diffuses to ECF and into blood
Alkaline tide
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gastric secretion

17. Mechanism of Acid secretion
H2O passes through cell and into canaliculi by OSMOSIS
Final secretion from the canaliculi contain
HCL at a conc of 150 to 160 mEq/L
KCl at conc of 15 mEq/L
Small amount of NaCl
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gastric secretion

18. CO2
CO2
H20
CO2 +
OH- H+
HCO3-
HCO3- K+ H+ K+ K+ K+
Na+
Na+ K+ K+
Na+
Na+
Cl-
Cl-
Cl-
H20
H20
H20

19. Pepsinogen Secretion Precursor of pepsin Produced by the Chief Cells
Stored in secretory granules
Vagal stimulation, Histamine, Gastrin
Cause preformed granules to be released into lumen
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gastric secretion

20. Intrinsic Factor Mucoprotein Essential for vitamin B12 absorption
Secreted by parietal cells
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gastric secretion

21. Control of Gastric Acid Secretion
Basal secretion
During fasting gastric juice secretion occurs
Postprandial
Cephalic, Gastric and Intestinal phases
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gastric secretion

22. Cephalic Phase Before food gets into the stomach
Sight , smell, thought, taste, hunger,appetite center
Cause reflex stimulation of gastric secretion
This phase of secretion
Accounts for 20% of total gastric secretion associated with eating a meal
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gastric secretion

23. Gastric Phase Presence of food in the stomach excite
Stretch receptors, chemo-receptors
Local enteric reflexes
Gastrin production
All these lead to stimulation of gastric secretion
Gastric phase of secretion
Account for 70% of total gastric secretion associated with eating a meal
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gastric secretion

24. Intestinal Phase Presence of food in the intestines
Release of Gastrin by duodenum
Continue to stimulate secretion of some gastric juice
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gastric secretion

25. Control of Gastric Acid Secretion
Neural mechanisms
Stimulation of vagus
Stimulates intramural plexuses
Which then stimulates PARIETAL, CHIEF, MUCUS cells
Neurotransmitter is Acetylcholine
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gastric secretion

26. Control of Gastric Acid Secretion
Vagal stimulation increases secretion by
Stimulating histamine releasing cells
Histamine then diffuses to stimulate parietal cells
Vagal stimulation activates antral G – cells
Produce Gastrin
Gastrin acts on parietal and chief cells
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gastric secretion

27. Control of Gastric Acid Secretion
Humoral
Gastrin
Secreted by G - cells
Peptide G34, G17
G17 more abundant and potent than G34 for acid secretion
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gastric secretion

28. Control of Gastric Stimulation
Stimulus for Gastrin secretion
Vagus
Secretagougues (AA,peptides, alcohol,caffeine,Ca++
Distension of stomach
Gastrin release intracellular Ca++
Promote proton pump
Cl- channel insertion
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gastric secretion

29. Control of Gastric Acid Secretion
Histamine
Enterochromaffin cells
Mast cells
Acts on H2 receptors
Increases cAMP
This then promote proton pump function
Increases H+ secretion
H2 receptor blockers
Cimetidine etc
Prostaglandin E1, E2 inhibit Histamine release
Pentagastrin stimulates HCl and Gastrin release
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gastric secretion

30. Ca++ Gastrin receptor Ca++ Ca++ Ach receptor H+ K+ cAMP
Histamine receptor H2
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gastric secretion

31. + + - - + - + + Ach Gastrin Histamine Somatostatin ECL Cells D- Cells
H2 receptor
Histamine
ATP - +
Adenyl cyclase -
D- Cells
cAMP +
Prot kinase K+
Somatostatin H+
G - Receptor
 Ca++
Ach - Receptor +

32. Inhibition of Gastric Juice Secretion
Acidity of gastric juice to pH <3.0
Gastrin mechanism is blocked
Enterogastric reflex
Presence of food in SI
Distension, acidity, FA, AA
Secretin, cholecystokinin
Oppose stimulatory effect of Gastrin
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gastric secretion

33. Enterogastric Reflex CCK GIP gastric inhibitory peptide
Initiates enterogastric reflex
Slows gastric emptying
Inhibit gastric secretion
GIP gastric inhibitory peptide
Inhibit Histamine
VIP vasoactive Intestinal peptide; somatostatin
Have moderate inhibitory effects on gastric secretion
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gastric secretion

34. Gastric Mucosal Barrier
Protect the gastric lining cells from
Damage by intra-luminal HCL
Autodigestion
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gastric secretion

35. Gastric Mucosal Barrier
Compact arrangement of epithelial cells with TIGHT JUNCTION
Epithelial cells secrete bicarbonate (under influence of prostaglandin)
Thick layer of adherent MUCUS (alkaline mucus) 1 mm thick
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gastric secretion

36. Gastric Mucosal Barrier
Regenerative capacity of mucosa
Trophic effect of Gastrin
High turn over rate:
Entire mucosa replaced within 3 days
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gastric secretion