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What is True about iron absorption are all, except ? and explain in detail?
Ans. is 'd' i.e., Pancreatic secretions improves the absorption Iron absorption Iron is absorbed from upper small intestine mainly duodenum. In diet iron occurs in two forms, haeme iron and inorganic (non-haeme) iron. Haem iron is better absorbed than inorganic iron, but the major fraction of diet is inorganic iron. Inorganic iron is mostly in ferric form; needs to be reduced to ferrous form because iron is absorbed in ferrous form. After absorption ferrous form is once again oxidized to ferric form inside enterocytes. A fraction of absorbed iron is rapidly delivered to plasma transferrin. However, most of the iron is deposited in the enterocytes as ferritin, some to be transferred more slowly to plasma transferrin, and some to be lost when senescent mucosal cells (enterocytes) are sloughed into the intestine. Iron absorption is regulated according to the demand, e.g., when there is iron deficiency, absorption increases. This regulation is mediated by "iron metabolism regulatory hormone", i.e., hepcidin that inhibit iron absorption. When there is iron deficiency, concentration of hepacidin falls and there is increase iron absorption. Hepacidin also decreases release of iron from storage sites. Transpo and storage of iron Iron is transpoed is blood in combination with a glycoprotein transferrin. Iron is transpoed into cells through attachment of transferrin to specific membrane bound receptors. Iron is stored as ferritin (major storage form) or haemosiderin. Ferritin is a complex of iron and apoferritin (iron + apoferritin ferritin). Iron is mainly stored in reticulo-endothelial cells monocytes/macrophages of liver, spleen, bonemarrow. It is also stored in hepatocytes (parenchymal cells of liver) and myocytes of skeletal muscles. Note : Iron is stored in ferritin in ferric form.