Iron is predominantly absorbed in -
Ans. is 'b' i.e., Duodenum IMPORTANT FACTS ABOUT ABSORPTIONo Absorption pattern of duodenum and jejunum is almost same. Following mentioned nutrients are absorbed both in duodenum and jejunum, however their absorption differs quantitatively : -Mainly absorbed in duodenum : - Calcium. Iron.Mainly absorbed in jejunum : - Amino acids, water soluble vitamins (B1. B2, B3, B5, B6, Biotin and VitaminC), fat soluble vitamins (A, E, D, K), Fats (Triglycerides, Cholesterol), Sugars (monosaccharides, disaccharides), water, NaCl (electrolytes).o Following are absorbed in the Ileum: - Bile & bile salts. Vitamin B12, Na+, water.# Vitamin B12. (cyanocobalamine) is absorbed in the ileum. Intrinsic factor (of castle) is necessary for its absorption IF is secreted by oxyntic cells of stomach. In the lumen of the small intestine, IF forms a complex with vitamin B12. Vitamin B12-IF complex binds with a specific receptor on the surface of the epithelial ceils of the ileum r. Vitamin B12 is transported into the enterocytes leaving behing IF at the brush border.o Following are absorbed in colon : - Water and electrolytes (Na & Cl )Water and electrolyte absorptiono Water and electrolytes need no digestion and are absorbed as such. There is approximately 9 liters of water input: Ingested water: 2.0 litres, Saliva: 1.5 litres, gastric juice: 2.5 litres, bile 0.5 litre, pancreatic juice: 1.5 litres, and small intestine secretions 1.0 litre. Out of these 9 litres, 7.7 litres (85%) is absorbed in small intestine and 1.0 - 1.5 litres (5-10%) is absorbed in large intestine (colon). Total 8.8 litres of water is absorbed and 0.2 litre is excreted in feces. In small intestine, most of the water is reabsorbed in the jejunum.o Na+ and Cl. are also absorbed maximally in jejunum with some absorption in colon.
Stomach
Duodenum
Colon
Ileum
Digestion and Absorption