1. Gastrointestinal physiology 2 M.Bayat Ph.D Principles of GI secretion,salivary, esophageal & gastric secretion

3. Secretion of Saliva

5. Functional Anatomy of the Salivary Glands There are three pairs of major salivary glands: Submandibular 70% mix Parotid 20% serous Sublingual 5% mucous small buccal glands 5% mucous Function Lubrication Digestion Protection

6. Acinus +duct= salivon (functional unit)

8. Iso-osmotic Hyp-osmotic Water absorption lesser than Na Cl absorption

9. increase flow rate increase HCO3 production and secretion NaCl=15mEq =1/7 to 1/10 plasma K=30mEq=7 time Hco3=50-70mEq= 2-3 time more than plasma

10. Sympathetic stimulation First: can also increase salivation a slight amount more amylase secretion Second: blood vessel contraction and decrease saliva parasympathetic stimulation Increase more water and electrolyte moderately dilate the blood vessels.

11. Hcl which is almost exactly isotonic with the body fluids. The pH of this acid is about 0.8

13. Secretions from the Oxyntic (Gastric) Glands mucus pepsinogen hydrochloric acid and intrinsic factor. IF HCL Pepsin پپسین برای هضم پروتین ضروری نیست. پپسین اندوپپتیداز است یعنی پروتین را به زنجیرهای کوچکتر می شکند.

14. parietal cell (also called oxyntic cell) canaliculi 7.4 0.8 PH=1 7.4

16. Secretion of HCL -cl secretion actively -Na absorption actively -40 to -70 millivolts in the canaliculus - diffusion K,Na -H secretion actively -K, absorption actively

17. Secretion and Activation of Pepsinogen. Pepsinogen has no digestive activity Contact with hydrochloric acid and pepsinogen convert to pepsin Pepsin functions as an active proteolytic enzyme in a highly acid medium (optimum pH 1.8 to 3.5) but above a pH of about 5 it has almost no proteolytic activity and becomes completely inactivated

18. Pyloric Glands contain mostly mucous cells These cells secrete a small amount of pepsinogen secrete the hormone gastrin,

19. Stimulation of Gastric Acid Secretion Acetylcholine, histamine, and gastrin are the three physiological agonists of HCI secretion Acetylcholine is released near parietal cells by cholinergic nerve terminals. Gastrin is produced by G cells in the mucosa of the gastric antrum and the duodenum and reaches parietal cells via the bloodstream. Histamine, a paracrine agonist, is released from enterochromaffin-like (ECL) cells in the gastric mucosa and diffuses to the parietal cells.

20. GIP VIP Secretin

21. Regulation of Pepsinogen Secretion stimulation of the peptic cells by (1) acetylcholine released from the vagus nerves or from the gastric enteric nervous plexus (2) acid in the stomach

22. کوله سیستوکینین از سلولهای I مخاط دوازدهه و ژژونوم ترشح می شود فراورده های تجزیه چربی و پروتئین محرک ترشح کوله سیستوکینین است اثرات cck = انقباض کیسه صفرا - مهار حرکات معده و اسید معده - افزایش ترشحات آنزیمی لوزالمعده سکرتین از سلولهای s مخاط دوازدهه ترشح شده شیره اسیدی معده محرک ترشح سکرتین است اثرات سکرتین = مهارحرکات معده و اسید معده افزایش ترشح بیکربنات لوزالمعده باعث خنثی شدن اسید می شود. GIP از مخاط قسمت فوقانی روده کوچک ترشح شده اسیدهای چرب و اسیدهای آمینه و کربو هیدرات عامل ترشح GIP اثرات = کاهش فعالیت حرکتی معده

23. Regulation by CCK (Cholecystokinin) CCKCCK gall bladder  Bile FOOD + - liver + fats & peptides bile & enzymes fat & protein digestion - HCl  2. Duodenal Response to Food CCK from I cell in duodenum and jejunum Increase pancreatic enzyme secretion

24. D. Duodenal Integration & Control: 1. Response to Acidity Regulation by Secretin HCl + NaHCO 3 NaCl + CO 2 + H 2 O + + - + gall bladder liver HCl   motility NaCl + H 2 O HCO 3 HCl NaHCO 3 Secretin Secretin from S cell in duodenum and jejunum Increase pancreatic bicarbonate secretion

25. Phases of Gastric Secretion 20 % 70 % Gastrin

26. Inhibition of Gastric Secretion by Other Post- Stomach Intestinal Factors Distention, acid, fat, protein breakdown products, hyperosmotic or hypo-osmotic fluids, or any irritating factor in the upper small intestine causes release of several intestinal hormones: secretin gastric inhibitory peptide, GIP Vasoactive intestinal polypeptide VIP Somatostatin SS