Which cell is the earliest stage in erythropoiesis?

Which cell is the earliest stage in erythropoiesis?

• A. Rubriblast
• B. Rubricyte
• C. Reticulocyte
• D. Erythrocyte

Answer: (A)

The earliest stage in erythropoiesis is the rubriblast. This cell marks the first erythroid precursor in the bone marrow. It is relatively large with a round, prominent nucleus and finely dispersed chromatin, and its cytoplasm is very basophilic because it is packed with ribosomes for ramping up protein synthesis, including hemoglobin. It often undergoes mitosis, laying the groundwork for the erythroid series. As maturation continues, it becomes progressively smaller with changes in cytoplasm color and chromatin, moving through prorubricyte and rubricyte stages, then to metarubricyte, followed by reticulocyte, and finally the mature erythrocyte. The later stages—rubricyte, reticulocyte, and especially the mature erythrocyte—reflect increasing hemoglobin content and eventual loss of a nucleus, which is not yet the case for the rubriblast.

The earliest stage in erythropoiesis is the rubriblast. This cell marks the first erythroid precursor in the bone marrow. It is relatively large with a round, prominent nucleus and finely dispersed chromatin, and its cytoplasm is very basophilic because it is packed with ribosomes for ramping up protein synthesis, including hemoglobin. It often undergoes mitosis, laying the groundwork for the erythroid series. As maturation continues, it becomes progressively smaller with changes in cytoplasm color and chromatin, moving through prorubricyte and rubricyte stages, then to metarubricyte, followed by reticulocyte, and finally the mature erythrocyte. The later stages—rubricyte, reticulocyte, and especially the mature erythrocyte—reflect increasing hemoglobin content and eventual loss of a nucleus, which is not yet the case for the rubriblast.