The digestive system is made up of is a group of organs working together to convert food into energy and basic nutrients to feed the entire body. This is called the digestive tract which is made from, in descending order, the mouth, oesophagus, stomach, small intestine, large intestine, rectum, and anus. All these organs are lined with a thin layer of “skin” called the mucosa. If this layer, from one person, was spread out it would cover a whole tennis court, yet it is only a quarter of the thickness of a piece of paper. The digestive tract also contains a layer of smooth muscle that helps break down food and move it along the tract.