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  • 1. OVERVIEW OF GASTROINTESTINAL FUNCTION & REGULATION (Shih-Che Huang)
    • OBJECTIVES
  • 2. Understand gastrointestinal function
    • structure of the gastrointestinal tract
  • 3. major gastrointestinal secretions

4. major hormones, peptides, and neurotransmitters 5. enteric nervous system and splanchnic circulation 6. Organization of the wall of the intestine into functional layers 7. structure of intestinal villi and crypts 8. Regulation of salivary secretion parasympathetic nervous system ACh, acetylcholine. 9. Anatomy of the stomach 10. Structure of a gastric glandfrom the fundusand body of the stomach 11. ECL (enterochromaffin-like) cells

  • More than 15 types of hormone-secretingenteroendocrine cells
    • in the mucosa of the stomach, small intestine, and colon.
  • 12. G cells, S cells, etc.
  • Others manufacture serotonin or histamine and are calledenterochromaffinorenterochromaffin-like (ECL) cells

13. Contents of Normal Gastric Juice (Fasting State )

  • Cations: Na+, K+, Mg2+, H+ (pH 1.0)

14. Anions: Cl, HPO4 2, SO4 2 15. Pepsins 16. Lipase 17. Mucus 18. Intrinsic factor 19. Intrinsic factor absorptionof vitamin B12 20. Regulation of gastric acid and pepsin secretion (SST somatostatin ) 21. Parietal cell receptors 22. Ion transport proteins of parietal cells 23. Clinical Box 1Peptic Ulcer Disease

  • Breakdown of mucosa barrier
  • Infection with the bacteriumHelicobacter pylori disrupts this barrier

24. Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs)

    • inhibit the production of prostaglandins
  • 25. decrease mucus and HCO3 secretion

26. Clinical Box 1 Peptic Ulcer Disease

  • Inhibition of acid secretion
    • cimetidine
    • block the H2 histamine receptors

omeprazole(proton pump inhibitor )

  • inhibit H+K+ ATPase on parietal cells
  • H. pylorican be eradicated with antibiotics

27. NSAID -induced ulcers

    • stopping the NSAID

28. PANCREATIC SECRETION 29. Principal Digestive Enzymes ( )

  • Stomach

30. Pepsins Proteins Polypeptides

  • Pancreas

31. TrypsinProteinsPolypeptides 32. LipaseTriglyceridesMonoglycerides, fatty acids 33. AmylaseStarchDextrins, maltotriose, maltose 34. Liver, gallbladder , and pancreas 35. Human bile acids 36. Lipid digestionand passage to intestinal mucosa 37. circulation of bile acids 38. Daily Water Turnover (mL) in the Gastrointestinal Tract

  • Ingested 2000

39. Endogenous secretions7000

    • Salivary glands 1500
  • 40. Stomach2500

41. Pancreas1500

  • Total input9000

42. Reabsorbed 8800

    • Jejunum 5500, Ileum 2000, Colon 1300
  • Balance in stool200

43. NaCl absorption in the small intestine and colon 44. Sodium absorption in the colon 45. Chloride secretion in the small intestine and colon 46. Lubiprostone ( )

  • Lubiprostone is an oral fatty acid that activates chloride channels on the intestinal epithelial cells, secreting chloride and water in the gut lumen
    • improve constipation

47. Clinical Box2 A40 y/o male patient with Epigastric pain for 1 day

  • Chronic alcohol intake

48. Pain was severe; moving would aggravate ; bending forward relieved pain 49. Vomiting 50. Clinical Box2 Acute pancreatitis( )

  • Lipase6597 IU/L(normal < 100 IU/L)

51. Amylase1627 IU/L(normal < 200 IU/L) 52. Admission diagnosis :ACUTE PANCREATITIS 53. Clinical Box2 Acute pancreatitis ( )

  • premature activation of zymogens( )

54. ASSOCIATED FACTORS( )

    • Gallstones ( )
  • 55. Alcohol ( )

56. Polypeptides in Gastrointestinal Tract

  • Gastrin (produced by G cells in antrum)
    • acid secretion
  • Cholecystokinin(cells in the mucosa of the upper small intestine)
    • stimulation of pancreatic enzyme secretion
  • Secretin (S cells in the glands of the mucosa of the upper small intestine)
    • bicarbonate by the duct cells of the pancreas and biliary tract

57. Sites of production of the five gastrointestinal hormones along the length of the gastrointestinal tract 58. GLP-1 (glucagon -like peptide 1) ( ) 59. MOTILIN -Migrating motor complexes (MMCs) 60. ENTERIC NERVOUS SYSTEM

  • myenteric plexus( )
    • between the outer longitudinal

and middle circular muscle layers

  • submucous plexus( )
    • between the middle circular layer

and the mucosa 61. ENTERIC NERVOUS SYSTEM

  • myenteric plexus
    • motorcontrol
  • submucous plexus
    • glandular epithelium, intestinal endocrine cells, and submucosal blood vessels
  • 62. intestinal secretion

63. ENTERIC NERVOUS SYSTEM

  • Neurotransmitters

64. acetylcholine, norepinephrine, serotonin,-aminobutyrate (GABA), the gases NO and CO, peptides 65. Some of these peptides also act in a paracrinefashion or enter the bloodstream , becoming hormones 66. most of them are also found in the brain 67. EXTRINSIC INNERVATION

  • Parasympathetic cholinergic activity
    • increasing the activity of intestinal smooth muscle
  • Sympathetic noradrenergic activity
    • decreasing the activity of intestinal smooth muscle
  • 68. causing sphincters to contract

69. GASTROINTESTINAL (SPLANCHNIC) CIRCULATION 70. SUMMARY

  • Gastrointestinal functions are regulated in an integrated fashion by endocrine, paracrine, and neurocrine mechanisms.

71. Hormones and paracrine factors are released from enteroendocrine cells in response to signals coincident with the intake of meals. 72. SUMMARY Brain gut axis

  • The enteric nervous system conveys information from the central nervous system to the gastrointestinal tract, but also often can activate programmed responses of secretion and motility in an autonomous fashion.

73. SUMMARY Portal system

  • The intestine has an unusual circulation.

74. The majority of its venous outflow does not return directly to the heart, but rather is directed initially to the liver via the portal vein. 75. Reference

  • Ganongs Review of Medical Physiology
    • McGraw Hill; 23rd ed, 2010
  • 76. KE Barrett, SM Barman, S Boitano, HL Brooks
  • Harrison's Principles of Internal Medicine
    • McGraw-Hill; 17 edition, 2008
  • 77. Fauci AS, Braunwald E, Kasper DL
  • Sleisenger and Fordtran's Gastrointestinal and Liver Disease: Pathophysiology, Diagnosis, Management
    • M Feldman, LS Friedman, LJ Brandt
  • 78. Saunders; 9th ed, 2010