The diagram shows the structure of small intestine. Please answer the question: (1) _ _ _ _ _ _ and _ _ _ _ _ of small intestine increase the absorption area of small intestine. (2) There are three kinds in small intestine. The small intestine is the main place for digesting food and absorbing nutrients. It is very long, about 5 ~ 6m long. There are annular folds on the inner wall of the small intestine, and there are small intestinal villi on the folds, which increases the area for digesting and absorbing nutrients. There are abundant capillaries in the villi of the small intestine, and its wall is only composed of a layer of epithelial cells, which is beneficial to absorbing nutrients. There are intestinal glands in the small intestine, which can secrete intestinal juice, which contains digested sugars and fats. Pancreatic juice secreted by pancreas flows into duodenum of small intestine through pancreatic duct.

So: (1) Small intestinal folds and villi increase the absorption area of small intestine.

(2) There are three digestive juices in the small intestine: pancreatic juice, intestinal juice and bile.

(3) The digestion of starch begins in the oral cavity, and salivary amylase in the oral cavity can decompose part of starch into maltose. When starch and maltose enter the small intestine, the pancreatic juice and intestinal juice in the small intestine contain enzymes for digesting sugar, so starch and other sugar substances are completely digested into glucose in the small intestine; Protein's digestion starts from the stomach. When protein in food enters the stomach, it enters the small intestine after preliminary digestion under the action of gastric juice. Pancreatic juice and intestinal juice in the small intestine contain enzymes for digesting protein. Under the action of these enzymes, protein is completely digested into amino acids. The digestion of fat begins in the small intestine. Pancreatic juice and intestinal juice in the small intestine contain enzymes for digesting fat. At the same time, bile secreted by the liver also enters the small intestine. Although bile does not contain digestive enzymes, it can emulsify fat and promote the digestion of fat. Fat is completely decomposed into glycerol and fatty acids under the action of these digestive juices.

Therefore, the answer is: (1) plica; Small intestinal villi.

(2) pancreatic juice.

(3) glucose; ? Amino acids; ? Glycerol and fatty acids.