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In mammals, it may be the principal site for iron absorption. The duodenum precedes the jejunum and ileum and is the shortest part of the small intestine. In human beings, the duodenum is a hollow jointed tube about 25–38 centimetres (10–15 inches) long connecting the stomach to the middle part of the small intestine.
The small intestine or small bowel is an organ in the gastrointestinal tract where most of the absorption of nutrients from food takes place. It lies between the stomach and large intestine, and receives bile and pancreatic juice through the pancreatic duct to aid in digestion. The small intestine is about 5.5 metres (18 feet) long and folds ...
The lining of the jejunum is specialized for the absorption by enterocytes of small nutrient particles which have been previously digested by enzymes in the duodenum. Once absorbed, nutrients (with the exception of fat, which goes to the lymph) pass from the enterocytes into the enterohepatic circulation and enter the liver via the hepatic ...
Polysaccharidases and disaccharidases in the glycocalyx break down large sugar molecules, which are then absorbed. Glucose crosses the apical membrane of the enterocyte using the sodium-glucose cotransporter. It moves through the cytosol (cytoplasm) and exits the enterocyte via the basolateral membrane (into the blood capillary) using GLUT2.
In the small intestine, the larger part of digestion takes place and this is helped by the secretions of bile, pancreatic juice and intestinal juice. The intestinal walls are lined with villi, and their epithelial cells are covered with numerous microvilli to improve the absorption of nutrients by increasing the surface area of the intestine ...
Intestinal glands are found in the epithelia of the small intestine, namely the duodenum, jejunum, and ileum, and in the large intestine (colon), where they are sometimes called colonic crypts. Intestinal glands of the small intestine contain a base of replicating stem cells , Paneth cells of the innate immune system , and goblet cells , which ...
The small intestine tract: This is where absorption takes place. [2] [3] [4] The brush borders of the intestinal lining are the site of terminal carbohydrate digestions. The microvilli that constitute the brush border have enzymes for this final part of digestion anchored into their apical plasma membrane as integral membrane proteins.
The following enzymes/hormones are produced in the duodenum: secretin: This is an endocrine hormone produced by the duodenal "S cells" in response to the acidity of the gastric chyme. Cholecystokinin (CCK) is a unique peptide released by the duodenal "I cells" in response to chyme containing high fat or protein content.