The small intestine is divided into three regions: duodenum, jejunum, ileum. Throughout the small intestine, chyme is mixed and propelled by segmentation and peristalsis. Segmentation involves contraction of circular muscle at random spots in the small intestine to mix its contents. Materials move materials down the small intestine and into large intestine by peristalsis, a moving wave of contraction identical to that in swallowing.
In the duodenum, pancreatic enzymes continue the digestion of macronutrients. Carbohydrates are digested to disaccharides and proteins to small peptides. Triglycerides are digested to monoglycerides and fatty acids. After digestion and absorption, the remaining undigested materials enter the cecum of the large intestine through the ileocecal valve.
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