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Gi function Gi function Presentation Transcript

  • OVERVIEW OF GASTROINTESTINAL FUNCTION & REGULATION 簡介 胃腸功能及其調節     黃士哲 (Shih-Che Huang)
    • OBJECTIVES 教學目標
    • Understand gastrointestinal function
      • structure of the gastrointestinal tract 胃腸構造
      • major gastrointestinal secretions 胃腸分泌
      • major hormones, peptides, and neurotransmitters 荷爾蒙 生肽 神經傳導物質
      • enteric nervous system and splanchnic circulation 腸神經系統 內臟循環
  • 胃腸構造 Organization of the wall of the intestine into functional layers
  • 腸構造 structure of intestinal villi 絨毛 and crypts 窩
  • Regulation of salivary secretion 唾液分泌 parasympathetic nervous system 副交感神經 ACh, acetylcholine.
  • Anatomy of the stomach 胃
  • Structure of a gastric gland 胃腺 from the fundus 底部 and body 體部 of the stomach
  • ECL (enterochromaffin-like) cells 腸親色素細胞
    • More than 15 types of hormone-secreting enteroendocrine cells 腸內分泌細胞
      • in the mucosa of the stomach, small intestine, and colon.
      • G cells, S cells, etc.
    • Others manufacture serotonin or histamine and are called enterochromaffin or enterochromaffin-like (ECL) cells
  • Contents of Normal Gastric Juice 胃液 (Fasting State 禁食 )
    • Cations: Na+, K+, Mg2+, H+ (pH 1.0)
    • Anions: Cl–, HPO4 2–, SO4 2–
    • Pepsins 胃蛋白酶
    • Lipase 脂肪酶
    • Mucus 黏液
    • Intrinsic factor 內因子
  • Intrinsic factor 內因子 absorption 吸收 of vitamin B12
  • Regulation of gastric acid 胃酸 and pepsin 胃蛋白酶 secretion (SST somatostatin 體抑制素 )
  • Parietal cell 壁細胞 receptors 受體
  • Ion transport 離子運輸 proteins of parietal cells 壁細胞
  • Clinical Box –1 Peptic Ulcer Disease 消化性潰瘍
    • Breakdown of mucosa barrier
    • Infection with the bacterium Helicobacter pylori 幽門螺旋桿菌 disrupts this barrier
    • Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) 消炎止痛藥
      • inhibit the production of prostaglandins
      • decrease mucus and HCO3 – secretion
  • Clinical Box –1 Peptic Ulcer Disease 消化性潰瘍
    • Inhibition of acid secretion 抑制 酸分泌
      • cimetidine
        • block the H2 histamine 組織氨 receptors 受體
      • omeprazole (proton pump inhibitor 質子幫浦抑制劑 )
        • inhibit H+–K+ ATPase on parietal cells
    • H. pylori 幽門螺旋桿菌 can be eradicated with antibiotics 抗生素
    • NSAID 消炎止痛藥 -induced ulcers
      • stopping the NSAID
  • PANCREATIC SECRETION 胰臟分泌
  • Principal Digestive Enzymes 酵素 ( 酶 )
    • Stomach 胃
    • Pepsins 胃蛋白酶 Proteins  Polypeptides 多生肽
    • Pancreas 胰臟
    • Trypsin 胰蛋白酶 Proteins  Polypeptides
    • Lipase 脂肪酶 Triglycerides  Monoglycerides, fatty acids
    • Amylase 澱粉酶 Starch  Dextrins, maltotriose, maltose
  • Liver, gallbladder 膽 , and pancreas 胰
  • Human bile acids 膽汁酸
  • Lipid digestion 脂質消化 and passage to intestinal mucosa 腸黏膜
  • circulation of bile acids 膽汁酸循環
  • Daily Water Turnover (mL) in the Gastrointestinal Tract
    • Ingested 入 2000
    • Endogenous secretions 分泌 7000
      • Salivary glands 1500
      • Stomach 2500
      • Pancreas 1500
    • Total input 9000
    • Reabsorbed 回收 8800
      • Jejunum 5500, Ileum 2000, Colon 1300
    • Balance in stool 200
  • NaCl absorption in the small intestine and colon
  • Sodium 鈉離子 absorption in the colon
  • Chloride 氯離子 secretion 分泌 in the small intestine and colon
  • Lubiprostone ( 便秘 新藥 )
    • 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 便秘
  • Clinical Box–2 A 40 y/o male patient with Epigastric pain 上腹痛 for 1 day
    • Chronic alcohol intake
    • Pain was severe; moving would aggravate 加重 ; bending forward relieved pain
    • Vomiting
  • Clinical Box–2 Acute pancreatitis ( 急性胰臟炎 )
    • Lipase 6597 IU/L (normal < 100 IU/L)
    • Amylase 1627 IU/L (normal < 200 IU/L)
    • Admission diagnosis 住院診斷 : ACUTE PANCREATITIS
  • Clinical Box–2 Acute pancreatitis ( 急性胰臟炎 )
    • premature activation of zymogens ( 酵素早期活化 )
    • ASSOCIATED FACTORS ( 常見 相關因素 )
      • Gallstones ( 膽結石 )
      • Alcohol ( 酒 )
  • Polypeptides 多生肽 in Gastrointestinal Tract
    • Gastrin 胃泌素 (produced by G cells in antrum)
      • acid secretion
    • Cholecystokinin 膽囊收縮素 (cells in the mucosa of the upper small intestine)
      • stimulation of pancreatic enzyme secretion
    • Secretin 分泌素 (S cells in the glands of the mucosa of the upper small intestine)
      • bicarbonate by the duct cells of the pancreas and biliary tract
  • Sites of production of the five gastrointestinal hormones along the length of the gastrointestinal tract
  • GLP-1 (glucagon 昇糖素 -like peptide 1) ( 糖尿病新藥 )
  • MOTILIN 運動素 - Migrating motor complexes (MMCs) 移動 式複合 運動
  • ENTERIC NERVOUS SYSTEM 腸神經
    • myenteric plexus ( 腸神經叢 )
      • between the outer longitudinal 縱走肌
    and middle circular muscle 環狀肌 layers
    • submucous plexus ( 黏膜下神經叢 )
      • between the middle circular layer 環狀肌
    and the mucosa 黏膜
  • ENTERIC NERVOUS SYSTEM 腸神經系統
    • myenteric plexus 腸神經叢
      • motor 運動 control
    • submucous plexus 黏膜下神經叢
      • glandular epithelium, intestinal endocrine cells, and submucosal blood vessels
      • intestinal secretion 分泌
  • ENTERIC NERVOUS SYSTEM 腸神經系統
    • Neurotransmitters 神經傳導物質
    • acetylcholine, norepinephrine, serotonin,  -aminobutyrate (GABA), the gases NO and CO, peptides
    • Some of these peptides also act in a paracrine 旁分泌 fashion or enter the bloodstream 血流 , becoming hormones
    • most of them are also found in the brain 腦
  • EXTRINSIC INNERVATION
    • Parasympathetic 副交感神經 cholinergic activity
      • increasing the activity of intestinal smooth muscle
    • Sympathetic 交感神經 noradrenergic activity
      • decreasing the activity of intestinal smooth muscle
      • causing sphincters to contract
  • GASTROINTESTINAL (SPLANCHNIC) CIRCULATION 內臟循環
  • SUMMARY
    • Gastrointestinal functions are regulated in an integrated fashion by endocrine, paracrine, and neurocrine mechanisms.
    • Hormones and paracrine factors are released from enteroendocrine cells in response to signals coincident with the intake of meals.
  • 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.
  • SUMMARY Portal system
    • The intestine has an unusual circulation.
    • 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.
  • Reference
    • Ganong’s Review of Medical Physiology
      • McGraw Hill; 23rd ed, 2010
      • KE Barrett, SM Barman, S Boitano, HL Brooks
    • Harrison's Principles of Internal Medicine
      • McGraw-Hill; 17 edition, 2008
      • Fauci AS, Braunwald E, Kasper DL
    • Sleisenger and Fordtran's Gastrointestinal and Liver Disease: Pathophysiology, Diagnosis, Management
      • M Feldman, LS Friedman, LJ Brandt
      • Saunders; 9th ed, 2010