What are the stages of erythropoiesis?

During erythropoiesis, a multipotent originator cell known as the hematopoietic stem cell (HSC) or haemocytoblast undergoes several maturation stages before transforming into a fully mature red blood cell, or erythrocyte. 

• Some hematopoietic stem cells differentiate into common myeloid progenitor (CMP) cells, which may go on to mature into red blood cells, platelets, or some types of white blood cells. 
• The CMP that eventually matures into a red blood cell (RBC) develops into a megakaryocyte-erythroid progenitor cell (MEP).
• MEPs progress through the following stages as they develop:
• Proerythroblasts: These are earliest identifiable precursors of red blood cells. They undergo rapid cell division. 
• Erythroblasts: These are larger cells with a centrally located nucleus. During this stage, the cells continue dividing and begin to synthesize hemoglobin. 
• Reticulocytes: Reticulocytes are immature red blood cells. They have an extruded nucleus and reticulated appearance when stained, which is due to the presence of residual ribosomal RNA. Reticulocytes are released from the bone marrow into the bloodstream. 
• Erythrocytes: Once in the blood stream, reticulocytes complete their maturation into erythrocytes within one to two days. Erythrocytes are fully mature red blood cells. 

It takes about a week for erythrocytes to fully mature.