Topic: Vitamins and minerals
Question: Describe with the help of a diagram absorption,storage and transport of iron.
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Brief overview of the absorption, storage and transport of iron in the body:
Absorption:
– Iron is absorbed in the duodenum and upper jejunum.
– Dietary iron exists in two forms – heme iron (from animal foods) and non-heme iron (plant-based).
– Heme iron is directly absorbed into the enterocytes.
– Non-heme iron is first converted to ferrous iron by the ferric reductase enzyme on the enterocytes.
– Ferrous iron then enters the enterocytes via the DMT1 transporter.
– Inside the enterocytes, heme containing hemoglobin is broken down releasing heme iron.
Storage:
– Iron is stored in a protein complex called ferritin in enterocytes and other tissues like liver, spleen and bone marrow.
– Liver is the major storage organ for iron in the body.
Transport:
– The enterocytes release iron into circulation via the ferroportin transporter.
– Hephaestin converts iron back to ferric form for transport.
– Plasma iron is bound to transferrin which keeps it soluble and delivers it to tissues.
– Bone marrow has transferrin receptors to internalize iron for hemoglobin synthesis in RBCs.
– Liver takes up and stores excess iron from circulation.
In summary, iron absorption occurs in the duodenum, storage happens in liver and other tissues, while plasma transferrin enables its transport and delivery to sites of utilization including bone marrow.
