An adult has on average 5 liters of blood and an erythrocyte count of 5 × 106/μl, giving a total erythrocyte count of 2.5 × 1013. Since the mean life span of an erythrocyte is normally 120 days, about 2 × 1011 new erythrocytes need to be formed daily to maintain this erythrocyte pool. For this to happen, about 20–30% of the medullary stem cells must be differentiated to cells of erythropoiesis. Different stages in maturation can be identified on the basis of cell morphology and biochemical capacity. The immature nucleated cells, such as preerythrobalsts and erythroblasts (macroblasts), with their high DNA, RNA and protein synthesizing capacity, ensure that there is adequate proliferation of erythrocyte precursors under stimulation by erythropoietin.
KeywordsPolycythemia Vera Neuraminic Acid Erythroid Progenitor Cell Hemoglobin Synthesis Mature Erythrocyte
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