Digestion takes place in the alimentary canal, also called the digestive tract or gastrointestinal tract. Basically, this structure is a tube that starts at the mouth and ends at the anus. Several vital organs and glands are connected to the alimentary canal and contribute digestive enzymes and other products to specific portions of the canal. Food is processed mechanically and/or chemically, depending on where it is in the alimentary canal. Food is chewed, or processed mechanically, by the teeth. At the same time, it is broken down by enzymes, or processed chemically, by saliva from the salivary glands. The esophagus transports food to the stomach, where mechanical and chemical processing continue. Food then enters the small intestine, where chemical processing is completed and the absorption of nutrients begins. The liver secretes substances required for the digestion of fats, and the gallbladder stores these substances before emptying them into the small intestine. The pancreas secretes enzymes and other substances into the small intestine to carry out chemical digestion. Finally, what is left of the food makes its way through the large intestine, where water is absorbed and feces are formed.