1. 消化和吸收 -2 （ Digestion & Absorption ） 蒋 正 尧 青岛大学医学院 生理学教研室 2008. 12

2. 胃体、胃窦粘膜内分泌、外分泌的功能

3. Properties – pH 0.9~1.5 – 1~2.5 L/day Major components – Hydrochloric acid – Pepsinogen – Mucus – Intrinsic factor 胃液（ Gastric juice ）

4. Hydrochloric acid Hydrochloric acid Secreted by the parietal cells Secreted by the parietal cells Output Output – Basal: 0~5 mmol/h ， 1-3L/d – Basal: 0~5 mmol/h ， 1-3L/d – Maximal: 20~25 mmol/h – Maximal: 20~25 mmol/h Acid sterilization Acid sterilization Activation of pepsinogen, partially digests dietary protein Activation of pepsinogen, partially digests dietary protein Promotion of secretin secretion Promotion of secretin secretion Assisted effect of iron and calcium absorption Assisted effect of iron and calcium absorption Makes dietary minerals soluble for absorption Makes dietary minerals soluble for absorption

5. HCl secretion Pumping H + against a gradient that is 2.5 million times more concentrated in the lumen

6. 盐酸的生理作用（ HCl secretion ） 激活胃蛋白酶原 ，提供酸性环境 刺激小肠粘膜分 泌促胰液素和 CCK ，进而促进 胰液、胆汁和小肠 液的分泌 杀灭胃内细菌； 可与 Ca 2+ 、 Fe 2+ 结合，促进其在小 肠内的吸收

7. HCl secretion

8. CFTR Alkaline tide CA:carbonic anhydrase

9. Blood Stomach Lumen CO 2 CO 2 + H 2 O Carbonic Anhydrase H 2 CO 3 H HCO 3 K ~ Cl pH<2 pH>7.4 H2OH2O

10. Stomach pH of stomach is low, 1 to 4; kills many bacteria and micro-organisms pH of stomach is low, 1 to 4; kills many bacteria and micro-organisms Achlorhydria, gastrectomy, GI dysfunction or disease ↑ risk of bacterial overgrowth in the intestines Achlorhydria, gastrectomy, GI dysfunction or disease ↑ risk of bacterial overgrowth in the intestines Protein digestion begins with pepsinogen which is converted to active pepsin in acidic stomach environment Protein digestion begins with pepsinogen which is converted to active pepsin in acidic stomach environment Chief cells secrete acid-stable gastric lipase, which has minor effect on shorter-chain triglycerides Chief cells secrete acid-stable gastric lipase, which has minor effect on shorter-chain triglycerides

11. 激活胃蛋白酶原

13. 粘液 - 碳酸氢盐屏障（ Mucus, Mucus- HCO 3 - barrier ） Secreted by the epithelial cells all over the mucosa and by the neck mucus cells in the upper portion of the gastric glands and pyloric glands Secreted by the epithelial cells all over the mucosa and by the neck mucus cells in the upper portion of the gastric glands and pyloric glands a layer ~500 μ m thick a layer ~500 μ m thick composed chiefly of mucins composed chiefly of mucins 由表层粘液细胞、颈粘 液细胞和幽门腺共同分 泌，主要成分是糖蛋白 润滑、保护胃粘膜，防 止胃酸、胃蛋白酶对粘 膜的损伤

15. Omepurazol Cimetidine Ranitidine

16. Intrinsic factor A high molecular weight glycoprotein, synthesized and secreted by the parietal cells The intrinsic factor binds to V B 12 and facilitates its absorption 内因子

17. 胃泌素

18. 胃液分泌的调节 （ Regulation of gastric secretion ） 胃液分泌的调节 （ Regulation of gastric secretion ） ExcitatoryInhibitory AChSomatostatin HistamineSecretin GastrinCCK GIP

23. 迷走神经在头期 胃液分泌有重要 作用

25. Intestinal phase Arrival of nutrients in duodenum  decreased gastric secretion and motility Arrival of nutrients in duodenum  decreased gastric secretion and motility Promotes secretion of CCK and secretin Promotes secretion of CCK and secretin - CCK promotes: - increased pancreatic enzyme secretion - gallbladder contraction and sphincter of Oddi relaxation - secretin promotes: - bicarbonate ion secretion (pancreas) - bile secretion

26. 消化期胃液分泌的时相 消化期胃液分泌的时相 头期胃期肠期 分泌量 总量的 30% 盐酸增多，胃蛋白 酶原含量多 总量的 50  60% 盐酸增多，胃蛋 白酶原含量少 总量的 5  10% 盐酸减少 刺激 食物色香味，咀嚼、 吞咽 胃扩张、氨基酸 等化学刺激 扩张、化学刺 激 机制 迷走神经， Ach, GRP 迷走 - 迷走反射, ENS 局部反射， 胃泌素较重要 胨诱发胃泌素 释放， CCK 等 负反馈

30. 胃运动及其调节 Motor Function of the Stomach 容受性舒张 Receptive relaxation 容受性舒张 Receptive relaxation – Storage function (1.0~1.5 L) – Storage function (1.0~1.5 L) – Vago-vagal reflex – Vago-vagal reflex 蠕动 Peristalsis 蠕动 Peristalsis – BER in the stomach – BER in the stomach 紧张性收缩 (tonic contraction) 紧张性收缩 (tonic contraction)

31. Motility Tonic contraction: sustained for minnutes or hours(sphincter, anterior portion of the stomach) Tonic contraction: sustained for minnutes or hours(sphincter, anterior portion of the stomach) Phasic contraction: with contraction-relaxation cycles lasting only for a few s (posterior portion of the stomach small intestine). Phasic contraction: with contraction-relaxation cycles lasting only for a few s (posterior portion of the stomach small intestine).

32. Peristalsis Muscular contractions that move food along throughout GI tract Muscular contractions that move food along throughout GI tract Gastric motility increases with the presence of gastrin and decreased under the influence of CCK, secretin and gastric inhibitory peptide (GIP) Gastric motility increases with the presence of gastrin and decreased under the influence of CCK, secretin and gastric inhibitory peptide (GIP)

33. Waves of smooth muscle contraction mix and propel the ingested contents of the gastric lumen, but only a small amount of the material enters the small intestine (duodenum) as a result of each wave cycle. 2 purposes ： moving food from the mouth to the anus. mixing food to break it into small patticles. Circular muscles contract just behind a bolus, pushes it forward (2-25cm/s) into a receiving Segment, where circular M. relaxed.

34. 胃排空 （ Emptying of the stomach ） 胃排空 （ Emptying of the stomach ） Emptying rate Emptying rate – Fluid > viscous – Fluid > viscous – Small particle > large particle – Small particle > large particle – Isosmotic > hyper- & hypo-osmotic – Isosmotic > hyper- & hypo-osmotic – Carbohydrates > Protein > Fat – Carbohydrates > Protein > Fat – Regular meal 4 ～ 6 hrs – Regular meal 4 ～ 6 hrs 影响因素及其调节 - 食物性质 - 肠胃反射 - 体液因素： 促胃液素加速胃排空， 促胰液素、 CCK 、 GIP 抑制胃排空

35. Effect of protein and fat on the rate of emptying of the human stomach. Subjects were fed 300-mL liquid meals.

36. Regulation of stomach emptying Gastric factors that promote emptying Gastric factors that promote emptying Gastric food volume Gastric food volume Gastrin Gastrin Duodenal factors that inhibit stomach emptying Duodenal factors that inhibit stomach emptying Enterogastric nervous reflexes Enterogastric nervous reflexes Fat Fat Cholecystokinin Cholecystokinin GIP GIP

37. Delivery of acid and nutrients into the small intestine initiates signaling that slows gastric motility and secretion which allows adequate time for digestion and absorption in the duodenum.

38. Integrated action of GI hormones in regulating digestion and utilization of absorbed nutrients. The dashed arrows indicate inhibition

40. 消化间期的胃运动 Migrating motor complex, MMC 每隔 90 分， 从胃至大肠， 清除食物残渣 、脱落细胞、 细菌 housekeeping

41. 谢谢 青岛大学 蒋正尧