Chyme moves through the small intestine by two different types of contractions: peristalsis and segmentation. Peristalsis is the rhythmic contractions that move chyme through the gastrointestinal tract. Segmentation involves localized contractions of small segments of the small intestine. These contractions mix the chyme with the secretions of the small intestine, gall bladder, and pancreas. The nutrients are brought into contact with the microvilli in the small intestine. The chyme is slowly propelled toward the ileocecal valve. Unlike peristaltic contractions, which are directional, the contractions of segmentation are not directional. Therefore, in order to keep the chyme moving downward, the duodenum contracts more frequently than the jejunum or ileum.