What is Vitamin-B12 deficiency is not seen in and explain in detail?
(A) Resection of jejunum # VITAMIN B12: normally binds to intrinsic factor, & the complex is taken up by cubilin, a high-affinity apolipoprotein in receptors in the distal ileum; Which triggers absorption of complex by endocytosis.> In the ileal enterocytes, the cyanocobalamin transferred to Transcobalamin-ll, a cyanocobalamin transport protein that transports the vitamin in plasma.> Cyanocobalamin deficiency is produced by Gastrectomy, with removal of the intrinsic factor-secreting tissue, & by pernicious anemia, a disease in which there is autoimmune destruction of the parietal cells> Vitamin B12 deficiency can also be produced by Diseases/resection of the distal ileum.> In totally gastrectomized patients, the intrinsic factor deficiency must be circumvented by parenteral injection of cyanocobalamin. Achlorhydria refers to a state of low gastric acid output in the stomach. Gastric acid is needed to split B12 from food proteins and salivary beveling proteins. Hence gastric acid absence creates a deficiency of vitamin B12