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Gatrointestinal secretions & motility

Applied Sciences Lecture Course. Gatrointestinal secretions & motility. Dr Ally Duncan Education Fellow & SpR in Anaesthesia Manchester Royal Infirmary. Learning objectives. Gastric secretion Regulation & Physiology of gastric acid production Gastric motility

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Gatrointestinal secretions & motility

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  1. Applied Sciences Lecture Course Gatrointestinal secretions & motility Dr Ally Duncan Education Fellow & SpR in Anaesthesia Manchester Royal Infirmary

  2. Learning objectives • Gastric secretion • Regulation & Physiology of gastric acid production • Gastric motility • Physiology of gastric emptying • Delayed emptying

  3. Anatomy of the stomach

  4. Which IS NOT a key function of the stomach? • Absorbing food • Secreting HCl • Storage • Mixing food

  5. Functions of the stomach • Storage • Preparing chyme for digestion in the bowel • Absorption of some water and lipid-soluble substances (alcohol and drugs)

  6. Functional components of stomach • Gastric secretions • Motility and emptying

  7. Regulation of functional components Neural • Enteric NS controls secretions and movement • Comprised of 2 plexuses: • Myenteric (Auerbach’s) • Submucosal (Meissner’s) • The plexuses are influenced by ANS Hormonal

  8. Regulation of gastric acid production

  9. Calcitonin gene related peptide 20% >70% of all acid production Regulation of Gastric acid production

  10. Somatostatin • Peptide hormone produced by neuroendocrine neurons in the hypothalamus • Secreted: stomach, intestine, pancreatic δ cells • Inhibits GH, TSH, Gastrin, CCK, secretin • Inhibits adenyl cyclase in parietal cells • Overall effect: ↓ gastric acid production

  11. Production of gastric secretions

  12. Gastric mucosa

  13. Which of the following is NOT a type of gastric epithelial cell? • Parietal cell • Chief cell • G cell • Epsilon cell

  14. Secretory epithelial cells • Mucous cells – secrete alkaline mucus • Parietal cells – secrete HCl • Chief cells – secrete pepsin • G cells – secrete gastrin

  15. Gastric secretions

  16. Production of HCl • Parietal cells • Energy dependant process • Production is influenced by: • Gastrin (CCK2 receptor) • Acetylcholine (M3 receptor) • Histamine (H2 receptor)

  17. Production of HCl

  18. Production of HCl

  19. Gastritis Acid production Vs Protective mucous production

  20. Management of gastritis/PUD Neutralisation of acid production • Pharmacological • Surgical • Vagotomy & Pyloroplasty • Partial gastrectomy Treatment of gastritis • Elimination of H.P

  21. Which of the following is NOT included in the treatment of H. Pylori? • Omeprazole • Lansoprazole • Ranitidine • Rabeprazole

  22. Gastric motility

  23. Regulation of functional components Neural • Enteric NS controls secretions and movement • Comprised of 2 plexuses: • Myenteric (Auerbach’s) • Submucosal (Meissner’s) • The plexuses are influenced by ANS Hormonal

  24. Gastrointestinal motility

  25. Gastrointestinal motility • GIT generates motility via SM subunits • Spontaneous cycles of slow wave potentials in specialised SM cells (Cajal) stimulate an AP • The longer the cycle, the more AP generated • The more APs, the greater the contraction • This process is Ca²+ dependent

  26. Gastric motility

  27. Gastric emptying • Intense peristaltic waves promote antral emptying • Forces a small amount of “chyme” into the duodenum • Pylorus acts as a pump and a sphincter • Water and other fluids pass with ease • Clear liquids are nearly empty within 2 hours

  28. Distension, irritation- acidity/osmolar change Fats in chyme Regulation of gastric emptying • Gastric: promote emptying • Stretch mediated in response to volume • Gastrin - promotes the pyloric pump • Duodenal: inhibit emptying • Neural • Intrinsic • Extrinsic • Endocrine • CCK • Secretin • GIP

  29. Overview of gastric emptying

  30. Which process DOES NOT affect gastric emptying? • Pregnancy • Anxiety • Pain • Tiredness

  31. Factors affecting gastric emptying • Food type - solids slower than liquids • Trauma • Anxiety • Opiates • Autonomic neuropathy: diabetes, CKD V • Intestinal obstruction

  32. Special circumstances

  33. Inlet to outlet shadow: Oesophagus, aorta, thoracic duct Achalasia cardia

  34. Achalasia of the cardia • Definition: Failure of the cardia to relax • Functional obstruction at the distal oesophagus • Dilated and filled with food • 40-70 years of age • Males=Females • Dysphagia, weight loss, chest pain, regurgitation • 5% develop squamous cell CA

  35. Paralytic ileus • Common in critical illness • Can be caused by: • Surgery, manual handling, intra-abdominal sepsis, opiates, epidural anaesthesia, SNS

  36. Paralytic ileus • Common • Signifies functional/organic pathology • Compromises breathing • Reduction in FRC→hypoxia • Gut mucosal ischaemia→bacterial translocation • Perforation: rarely

  37. Hunger “pangs” • Occur when stomach has been empty for 12-24 hours • Rhythmic peristaltic contractions of the body • Successive contractions may merge→ tetanic contractions lasting 2-3 minutes • More pronounced in the young • “Maximum intensity in 3-4 days • Gradually weaken

  38. Summary • Gastric secretions- acid production • Parietal cell • Gastrin, histamine and Ach • Proton pumps • Gastrointestinal motility • Factors affecting gastric emptying • Disorders of gastric emptying

  39. Any questions?

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