Every time you eat, you are sending the food that you just ate down the digestive system. This long tube joins your mouth to your stomach and then winds its way through the abdomen to the other end of the alimentary canal, the anus.
Your body cannot use food in the form that you swallow it. The digestive system uses mechanical processes (chewing and churning) and chemical processes (enzymes) to break food down into very small pieces.
In the mouth, food is chopped and ground by the teeth and moistened by saliva. In the stomach, it is churned around into a mushy soup and mixed with digestive juices, such as the bile and pancreatic juice. Saliva and the juices all contain substances called the enzymes. Enzymes are substances that help to digest food. As the food is passed out of the stomach and into the small intestine, more enzymes still continue to break down the food into even smaller particle, so that it is small enough to pass through the walls of the intestine into the blood.
Only the indigestible part of your meal will complete the whole journey through the digestive system and leave your body as faeces. Most of the meal is digested. Then the food is chemically changed, and taken inside the body and is used to nourish it in several ways.
Each lump of food being digested in moved along the digestive system by a process called peristalsis. The muscles in the walls of the alimentary canal squeeze together behind the lump to push it along. When all the nutrients are absorbed from the food, the reminder is passed out to the body.

See a video of the digestive system!