The differentiation of erythrocytes takes place over about 6 days within the extravascular cords of red bone marrow.
The stages involved include sequentially:
- primitive haemopoietic stem cell
- uncommited stem cell
- relatively large cell and nucleus
- mildly basophilic staining
- basophilic erythroblast: intensely basophilic staining due to large numbers of ribosomes producing haemoglobin
- polychromatophilic erythroblast:
- smaller cell and nucleus
- increasing amounts of haemoglobin, eosinophilic in nature, result in dual staining
- small nucleus
- large amounts of eosinophilic cytoplasm due to haemoglobin
- nucleus is extruded
- passes into blood to mature into final erythrocyte
Differentiation accompanies up to 4 mitotic divisions yielding up to 16 erythrocytes for each stem cell.