在解剖学上,胃肠道的两端向外开口,被看作是食物和水分通向机体的走廊。人们摄入的食物,种类繁多,性状不一,且有各种香料、酒精等刺激性物质,温度和酸碱度的变化也很大。即使在饥饿状态下,胃内也常含有酸性液体和胃蛋白酶,而且还经常有损伤胃粘膜的胆汁倒流入胃。十二指肠是食物和消化液必经之地,是四种性质不同的消化液(胃液、胰液、胆汁、十二指肠液)汇流之处,经常遭受机械性和化学性(特别是强烈的酸性和碱性)冲 Anatomically, the two ends of the gastrointestinal tract open outward and are seen as corridors of food and water leading to the body. People take in food, a wide range of different traits, and a variety of spices, alcohol and other irritating substances, temperature and pH changes are also great. Even in the hungry state, the stomach often contains acidic liquids and pepsin, but often also the gastric mucosa is infiltrated into the stomach. The duodenum, where food and digestive fluids go by, is a confluence of four different types of digestive fluids (gastric, pancreatic juice, bile, and duodenal fluid), often subject to mechanical and chemical (especially intense Acidic and alkaline) red