Explain the Small Intestine?
The small intestine is made up of three sections, the duodenum, the jejunum, and the ileum. Bile from the liver and pancreatic enzymes are released into the first section of the small intestine, the duodenum, where most of the overall digestion occurs although it is short - only about 25 cm. Their arrival triggers the production of mucus and the release of digestive enzymes from the glands at the base of projections called villi found in the mucus lining of the intestine. Villi function to expand the exposed surface area of the cell membranes in order to increase the rate of absorption of processed nutrients passing through the digestive tract. Each finger-like villus membrane surface is itself covered with millions of microvilli - even tinier finger-like projections of cell membrane, giving the small intestine a huge surface area for transport of nutrients. Enzymes secreted by the intestinal wall include lipases to split fats into glycerol and fatty acids; peptidases that break proteins down into amino acids; and maltase, lactase, and sucrase, that convert disaccharides into monosaccharides. The products of digestion are delivered to the circulatory system by a process called absorption. Absorption takes place through the villi into capillaries and lymph vessels called lacteals that line the intestine. Fatty acids formed in the interior space or lumen of the intestine diffuse into the mucosa, where triglycerides are synthesized and combined with cholesterol and phospholipids, then coated with protein to form water-soluble chylomicrons, which are carried into the lacteals and eventually into the blood stream near the heart through the large lymph duct called the thoracic duct. The products of digestion of sugars and proteins are carried by the capillaries to the liver, where the glucose is converted to glycogen for storage, and the rest of the nutrients are filtered for detoxification and then distributed by the blood stream to the rest of the body.