Major site for absorption of iron in GIT-
Correct Answer: Duodenum
Description: Ans. is 'a' i.e., Duodenum * Iron is absorbed from upper small intestine mainly duodenum. In diet iron occurs in two forms, haeme iron and inorganic (non-haeme) iron. Flaem 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 uiron 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. Factors affecting iron absorptioni)Decreasing absorption* By complexing (forming chelate) with iron: Phytate, phosphate, milk, EDTA, tetracycline.* By opposing reduction of ferric to ferrous form : Antacids, alkalies, pancreatic secretions.2)Increasing absorption* By enhancing reduction of ferric to ferrous form : Ascorbic acid, HCL, gastric secretions, citric acid.
Category:
Physiology
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