Upon reaching the ampulla of Vater in the middle of the duodenum, chyme is mixed with bile from the liver and gallbladder, as well as pancreatic juice produced by the pancreas. These secretions complete the process of chemical digestion that began in the mouth and stomach by breaking complex macromolecules into their basic units. Bile produced in the liver and stored in the gallbladder acts as an emulsifier, breaking lipids into smaller globules to increase their surface area. Pancreatic juice contains many enzymes to break carbohydrates, lipids, proteins and nucleic acids into their monomer subunits. For example, pancreatic lipase breaks triglycerides, or fats, into glycerol and fatty acids that can be absorbed into the bloodstream by the intestinal wall. These secretions are thoroughly mixed with the chyme by contractions of the duodenum until all of the digestible material is chemically digested.