The stages of red blood cell lineage development are presented in Diagram of hematopoiesis

• are the earliest precursors of red blood cells that are distinguished in bone marrow smears
• are large cells 15-20 μm in diameter
• have large rounded nuclei with some heterochromatin
• have a slightly basophilic cytoplasm

Proerythroblasts q.v. #1, #2, #3

• are of smaller size: 12-16 μm
• have more heterochromatin in nuclei
• have a highly basophilic cytoplasm due to a greater RNA content

Basophilic erythroblasts #1, #2, #3, #4

• are 10-12 μm in size
• nuclei are dense with large heterochromatin clumps
• progressively accumulate hemoglobin in their cytoplasm, thereby becoming stained as polychromatic, i.e. both by basic and acidic dyes

Polychromatophilic erythroblasts #1, #2, #3, #4

Proerythroblasts, basophilic and polychromatophilic erythroblasts are able to divide, so you may find there some mitotic stages #1, #2, #3

• have a small size of 8-10 μm
• have oxyphilic cytoplasm because of a higher hemoglobin content
• contain small, dense (pyknotic) nuclei that are often eccentric; finally, the nuclei are removed from the cytoplasm
• lose the potential to divide

Acidophilic erythroblasts q.v. #1, #2, #3, #4

• are somewhat larger than red blood cells: 7-8 μm
• have no nuclei as they are cell-derived structures
• there are some remnants of polyribosomes in the cytoplasm so reticulocytes are slightly more basophilic than red blood cells
• are transformed into red blood cells in the bone marrow; they may leave for the blood to mature finally; it takes 24-48 hours

• are final stage elements in erythrocytopoiesis
• have no nuclei
• have oxyphilic cytoplasm containing hemoglobin
• after bone marrow stage, they circulate in the blood stream for 100-120 days