Peristalsis pushes bile into the gallbladder from the cystic duct (muscle contractions that occur in orderly waves). Bile is then gradually concentrated by water absorption via the gallbladder's walls. This concentrated bile is stored in the gallbladder until it is required to digest the next meal. When you eat a fatty meal, your gallbladder stores some of the fat in bile. The muscle layer of the gallbladder functions as a pump when peristalsis moves bile through the cystic duct into the gallbladder. The muscle layer also acts as a reservoir if there is not enough food in the intestine to produce sufficient amounts of bile. As long as there is plenty of food in the intestine, the gallbladder keeps filling up with bile. When you eat a fatty meal, your gallbladder begins storing fat in bile immediately after you finish eating. By the time you start feeling hungry again several hours later, the fat-filled gallbladder has finished its job of preparing the next meal. At this point, the muscle layer of the gallbladder contracts, pushing the bile out through the cystic duct into the duodenum where it can be absorbed by the body through the lining of the small intestine.