动物生理学6.消化与吸收(五).ppt

6.6 Absorption 　　吸收：消化管腔内经过消化后的营养物质、水和无机盐类等透过消化管粘膜上皮进入血液和淋巴的过程。 6.6..1 吸收部位和途径 Absorption of nutrients, vitamins, electrolytes, and minerals occurs almost exclusively in the small intestine. The mucosa of small intestine is arranged in a series of annular fold that are lined by finger-like villi that increase the available absorptive surface to 300 times that of the equivalent flat surface area. In the small intestine, most absorption involves an active transport system through the brush border membrane. The exception are short chain fatty acids and other small liquid-soluble molecules that traverse the apical membrane by simple diffusion. 吸收的部位 主要吸收部位：小肠粘膜 为什么说小肠是吸收的主要部位？ 可被吸收的小分子物质 时间保证 吸收面积 通透性 小肠运动和绒毛舒缩 吸收的机制 被动转运 主动转运 6.6.2 Absorption of major nutrients in small intestine 　　小肠每日可吸收数百克糖，100克以上的脂肪，50－100克氨基酸，50－100克无机盐和6－8L水。需要时，上述吸收量可增加数倍。 Water and electrolytes Approximately 8 litter of water daily are absorbed in the small intestine, about 1.3 litter in the colon. This water is absorbed mainly by osmosis. Electrolytes are absorbed more readily from duodenum and jejunum than from ileum. Monovalent ions like Na+, K+, Cl－, HCO3－ are absorbed more rapidly than polyvalent ones, such as Ca+ and Mn+ 水、无机盐和维生素的吸收 扩散入细胞，Na+泵出粘膜细胞，伴随水的转运。 Ca2+的吸收 主要在十二指肠吸收。 主动吸收，但也有被动过程参与。 酸性环境、维生素D促进钙吸收。 脂肪酸、胆汁酸与钙结合形成水溶性复合物阻碍钙吸收。 Fe2+的吸收 方式：Fe2+ 机制：主动吸收 维生素C、胃酸促进铁吸收 Carbohydrates Complex polysaccharides and some disccharides are ultimately broken down in the intestinal tract into simpler forms---the monosaccharides, which are readily aborbed. Glucose and other hexoses (6-carbon sugars) and pantoses (5-carbon sugars) are readily absorbed from the duodenal and ileal mucosas into the blood capillaries. Glucose and galactose, are transported across the mucosa by an active process called carrier mediated transport. 吸收方式：单糖 吸收速度：葡萄糖、半乳糖＞果糖＞甘露糖 葡萄糖吸收机制：Na+的协同转运 途径：血液 Protein 方式：氨基酸与小分子肽 机制：载体介导（Na+依赖性） 途径：血液 lipid 脂肪：甘油三酯（甘油、脂肪酸） 类脂：胆固醇、胆固醇酯、磷脂、