The first section of the small intestine is called the duodenum. Chyme enters through a sphincter in little squirts as the stomach forms a squeezing motion to push the chyme through. In the small intestine is where most digestion occurs. Before this point, only carbs and proteins have been partially digested, and lipids or fats have not been digested at all.
From here the pancreas releases pancreatic juice into the small intestine, which has pancreatic amylase that breaks starch into maltose or sugar, much like the amylase found in saliva. Pancreatic juice also has bicarbonate to neutralize the acid in chyme from the stomach. Also in pancreatic juice is chymotrypsin and trypsin, which digest proteins into peptides, as well as lipase, which digests fats into glycerol and fatty acids.
The gallbladder contains bile, which is produced by the liver. The gallbladder releases bile into the duodenum, so it can emulsify fats, or break them into smaller drops. Digested fats are changed into glycerol and fatty acids.
The small intestine has many ridges called microvilli that increase its surface area. Here glucose and amino acids are moved into the intestinal cells by active transport, where blood capillaries can pick them up, and move them into cells. Glycerol and fatty acids, however, enter villi by diffusion and reassembling them into fat or triglycerides. Here the triglycerides combine with proteins and move into the lacteals so they can be transported into the lymphatic system.