Peristalsis is the term used to describe how muscle layers contract and expand in order to move food throughout the digestive system. From the mouth, the food goes through the esophagus, into the stomach, then through the small and large intestines until it finally comes out the rectum. During this process, the small intestine absorbs nutrients which are moved into the blood stream by way of “vili”, or small projections in the small intestines, which contain dedicated cells to assist in the process.