The picture shows the structure of human digestive system. Please answer the following questions: (1) Use the corresponding letters in the picture to represent the following digestive organs: Oral cav

The picture shows the structure of human digestive system. Please answer the following questions: (1) Use the corresponding letters in the picture to represent the following digestive organs: Oral cavity: _ _ _ _ _ _. The chemical system of the human body consists of the following parts:

(1) As can be seen from the figure, A salivary gland B pharynx C liver E appendix F anus G small intestine H large intestine I pancreas J stomach K esophagus L mouth.

(2) The stomach is a part of the digestive tract. An adult's stomach can hold about 2 liters of food and can temporarily store food. The stomach is cystic and has great extensibility. There is a well-developed muscle layer on the stomach wall, which can make the stomach peristalsis and grind and stir food when contracting. The gastric glands on the inner wall of the stomach can secrete a lot of gastric juice. The gastric juice is strongly acidic, and pepsin in it has a preliminary digestive effect on protein. Pepsin in gastric juice can transform protein into polypeptide.

(3) The small intestine is the longest in the digestive tract, about 5-6 meters long; There are many annular folds on the inner surface of the small intestine wall, and there are many villous protrusions on the folds, which are called small intestine villi. Because of the existence of annular folds and small intestinal villi, the absorption area of small intestine has greatly increased, reaching more than 200 square meters. The villus wall of small intestine is very thin and consists of only one layer of epithelial cells. There are abundant capillaries and lymphatic capillaries in villus, which is beneficial to the absorption of nutrients by small intestine. Therefore, the small intestine is the main organ for absorption. There are many digestive enzymes in the small intestine, which can digest starch, fat and protein, which is related to the digestive function of the small intestine.

(4) The salivary glands in the mouth can secrete digestive juice, and digestive enzymes can convert starch into maltose, so we have a sweet taste when chewing steamed bread.

So, the answer is: (1) l; k； j； c； h； G(2) temporary storage of food, grinding and stirring of food, digestion of food (3) main place for digestion and absorption (4) salivary glands in the mouth can secrete digestive juice, and digestive enzymes can convert starch into maltose.