Food moves through the digestive system via a process known as peristalsis. Involuntary muscles create a wavelike movement and food is passed along the alimentary canal from one organ to the next by these muscle contractions. In the mouth, saliva has the enzyme ptyalin which acts on starches. In the esophagus, the saliva continues to act on starch. The stomach has gastric juice with proteases which begin the chemical digestion of starch, in an acidic environment. In the small intestine, proteases, lipases and carbohydrate enzymes complete the chemical digestion of food in an alkaline environment, which is then absorbed through the tiny villi projecting from the small intestinal lining. Wastes and undigested materials go to the large intestine, where they are eliminated through the anus. Water is reabsorbed through the large intestinal lining. Accessory organs are the pancreas, which makes digestive enzymes for all food groups and the liver which makes bile, to emulsify fats.