Define the Functions of Small Intestine

What functions does the small intestine perform? Can you list a few? Tally your responses with the functions enumerated herewith. The small intestine secretes intestinal juice. Intestinal juice containing enzymes completes the digestion of carbohydrates, proteins and fats. The small intestine protects the body against infection by bacteria with the help of solitary lymph nodes and aggregated glands. The walls of villi of the small intestine are able to absorb glucose, amino acid, fatty acid, glycerol etc. These are the end-products of carbohydrate, protein and fat metabolism, as you may have already studied in the Nutritional Biochemistry Course. Glucose and amino acids are absorbed through blood capillaries. Fatty acids and glycerol are absorbed into lacteals or lymph capillaries. The surface area for absorption of nutrients is vastly increased by the circular folds of the mucus membrane and by the large number of villi.

The main function of the small intestine, as you may have read above, is to secrete intestinal juices which help in digestion. What substances/constituents are present in the intestinal juice? Can you tell? How does it aid in digestion?