Which normoblast is considered the most mature?

The orthchromic normoblast is recognized as the most mature stage in the development of red blood cells (erythropoiesis). At this stage, the cell exhibits a few key characteristics that indicate its maturity. The chromatin pattern becomes condensed and coarse, signaling the end of hemoglobin synthesis. This normoblast type also has minimal basophilia due to the decrease in RNA content as the cell shifts towards completing its maturation process.

During the preceding stages, such as the basophilic and polychromatic normoblasts, the cells still contain more RNA and exhibit more basophilic staining due to residual ribosomal RNA. The presence of significant amounts of hemoglobin production begins in the polychromatic normoblast stage, where the cell begins transitioning from blue-tinted cytoplasm to a more pinkish hue. However, it is the orthchromic normoblast that is just a step away from being a reticulocyte, marking it as the final stage of maturation before exiting the bone marrow into the peripheral blood, where it will further mature into a fully functional erythrocyte.