Final answer:
Enzymes and bile are transported into the duodenum, the first section of the small intestine, where they aid in digestion. The bile emulsifies fats, while pancreatic enzymes break down various macromolecules. The ileum, being the end portion of the small intestine, mainly absorbs vitamin B12 and bile salts.
Step-by-step explanation:
Enzymes and bile are carried by the pancreatic duct and bile duct into the duodenum. The duodenum is the first section of the small intestine immediately following the stomach, separated by the pyloric sphincter. It is in the duodenum where chyme from the stomach is mixed with bile and pancreatic juices. The bile, which is produced in the liver and stored in the gallbladder, contains bile salts that emulsify fats and aid in the absorption of fat-soluble vitamins. The pancreatic juices include enzymes that break down starches, disaccharides, proteins, and fats, creating an alkaline environment which neutralizes the acidic chyme coming from the stomach.
Bile is secreted into the duodenum through the common bile duct, while the pancreatic enzymes are transported through the pancreatic ducts. Absorption of nutrients predominantly occurs in the duodenum, but some absorption also takes place in the latter parts of the small intestine, the jejunum, and the ileum. However, the primary purpose of the ileum, the final part of the small intestine, is to absorb vitamin B12 and bile salts, with undigested or unabsorbed substances passing on to the large intestine.