Slow waves of smooth muscle contraction known as peristalsis flow down the length of the gastrointestinal tract to push chyme through the duodenum. Each wave begins at the stomach and pushes chyme a short distance toward the jejunum. It takes many peristaltic contractions over the course of an hour for chyme to travel through the entire length of the duodenum. Small regional contractions of the intestinal wall, known as segmentations, help to mix chyme with the digestive secretions in the duodenum and increase the rate of digestion. Segmentations also increase the contact of chyme with the mucosal cells to increase the absorption of nutrients through the intestinal wall.