The Small Intestine

The Small Intestine - • Mechanical digestion Segmentation...

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The Small Intestine The small intestine (small in diameter compared to the large intestine) is divided into three sections,  as shown in Figure :  The duodenum, about 25 cm (10 inches) long, receives chyme from the stomach through the  pyloric sphincter. Ducts that empty into the duodenum deliver pancreatic juice and bile from  the pancreas and liver, respectively. The jejunum, about 2.5 m (8 feet) long, is the middle section of the small intestine. The ileum, about 3.6 m (12 feet) long, is the last section of the small intestine. It ends  with the ileocecal valve (sphincter), which regulates the movement of chyme into the large  intestine and prevents backward movement of material from the large intestine. The functions of the small intestine include the following: 
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Unformatted text preview: • Mechanical digestion. Segmentation mixes the chyme with enzymes from the small intestine and pancreas. Bile from the liver separates fat into smaller fat globules. Peristalsis moves the chyme through the small intestine. • Chemical digestion. Enzymes from the small intestine and pancreas break down all four groups of molecules found in food (polysaccharides, proteins, fats, and nucleic acids) into their component molecules. • Absorption. The small intestine is the primary location in the GI tract for absorption of nutrients. The components of carbohydrates, proteins, nucleic acids, and water-soluble vitamins are absorbed by facilitated diffusion or active transport. They are then passed to blood capillaries....
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