Red Blood Cells - Erythropoiesis And The Dificiency Anaemias Flashcards
Erythropoiesis - sequence
Myeloid progenitor —> proerythroblast —> erythroblast
—> erythrocytes
Differentiation progresses —> self renewal and lineage plasticity decrease
Erythropoietin (EPO)
Growth factor
Glycoprotein that is synthesised in response to hypoxia
—> demand-supply feedback loop
Stimulates bone marrow to produce more red blood cells
2 major functions of iron
Oxygen transport in Haemoglobin
Mitochondrial proteins
Iron absorption
Absorbed in the duodenum
Haem iron (animal derived) - in ferrous form (Fe2+)
—> best absorbed form
Non-haem - ferric form (Fe3+)
—> requires action of reducing substances for absorption
Iron homeostasis
Excess iron potentially toxic to organs such as heart and liver
Only 1-2 mg per da absorbed from diet
Absorption of iron in gut heavily regulated according to body stores by hepcidin
What happens in response to high storage iron?
Liver secrets hepcidin
Absorption of iron from the gut and the release of storage iron is blocked
What happens in response to low storage iron?
Down regulation of hepcidin production
Increases Fe absorption and release
Vitamin B12 and folic acid
Necessary for the synthesis of thymidine
Deficiency inhibits DNA synthesis
—> bone marrow cells can grow but not divide
Absorption of vitamin B12
- B12 cleaved by HCl in stomach ands combines with intrinsic factor
- B12-IF binds to receptors in the ileum
What may B12 deficiency result from?
Inadequate intake (veganism)
Inadequate secretion of IF —> pernicious anaemia
Malabsorption —> e.g coeliac disease, surgery
Lack of acid in stomach —> achlorhydria
How are red blood cells destroyed?
Destroyed by phagocytise cells of the spleen (macrophages)
Iron from haem returns to bone marrow —> recycled
