Proerythroblast

Red blood cells (erythrocytes) develop from the multipotential myeloid stem cell (CFU-GEMM) which differentiates into the erythrocyte progenitor cell (CFU-E).

Proerythroblasts are produced directly from hematopoietic progenitor cell (CFU-E) under the influence of erythropoietin.

First recognizable precursor of red blood cells.

• Large cells (15 to 20 µm diameter)
• Large, round nucleus with a very fine chromatin
• Small amount of basophilic cytoplasm (pale blue to blue) as a result of ribosomes
• Capable of mitosis

Examples:

• Proerythroblast #1 (60x) [+]

• Proerythroblast #2 (60x) [+]

• Proerythroblast #3 (60x) [+]

• Proerythroblasts #4 (60x) [+]

Basophilic Erythroblast

Basophilic erythroblasts increase the production of ribosomes.

• Smaller cells (12 to 15 µm diameter)
• Round nucleus with a darker, coarse pattern of chromatin
• Very basophilic cytoplasm as a result of the large number of ribosomes
• Capable of mitosis

Examples:

• Basophilic Erythroblast #1 (60x) [+]

• Basophilic Erythroblast #2 (60x) [+]

• Basophilic Erythroblast #3 (60x) [+]

• Basophilic Erythroblast #4 (60x) [+] - mitotic cell

Polychromatic Erythroblast

Polychromatic erythroblasts begin producing large amounts of hemoglobin.

• Smaller cells (10 to 12 µm diameter)
• Round nucleus with more condensed chromatin
• Cytoplasm appears gray or pale blue from a mixture of basophilia (ribosomes) and eosinophilia (hemoglobin)
• Capable of mitosis

Examples:

• Polychromatic Erythroblast #1 (60x) [+]

• Polychromatic Erythroblasts #2 (60x) [+]

• Polychromatic Erythroblast #3 (60x) [+]

• Polychromatic Erythroblast #4 (60x) [+] - mitotic cell

Orthochromatic Erythroblast

Orthochromatic erythroblasts accumulate increasing amounts of hemoglobin. They lose their nuclei by extruding it from the cell.

• Smaller cells (8 to 10 µm diameter)
• Small, eccentric, pyknotic nucleus
• Cytoplasm ranges from gray (or light purple) to bright pink (hemoglobin)
• No longer capable of mitosis

Examples:

• Orthochromatic Erythroblast (60x) - cytoplasm is gray (compare to adjacent polychromatic erythroblast) [+]

• Orthochromatic Erythroblast (60x) - cytoplasm is pink-gray [+]

• Orthochromatic Erythroblast (60x) - cytoplasm is gray [+]

• Orthochromatic Erythroblast (60x) - a cell extruding its nucleus [+]

• Late Orthochromatic Erythroblast (60x) - cytoplasm is bright pink because it has lost most of its ribosomes before nucleus extrusion [+]

• Late Orthochromatic Erythroblast (60x) - a cell just before extrusion of the nucleus [+]

Also see EM 211 Orthochromatic Erythroblast.

Reticulocyte

Reticulocytes are formed when the nucleus is extruded from the cell. They slowly lose ribosomes and become mature red blood cells.

• Small cells (7 to 8 µm diameter)
• Nucleus absent
• Eosinophilic cytoplasm (hemoglobin) is slightly gray because of the remaining ribosomes

Examples:

• Reticulocytes (60x): [+]

• Reticulocyte (60x): [+]

A small number of reticulocytes are released from the bone marrow into the peripheral circulation.

Red Blood Cells

Red blood cells (or erythrocytes) are the final product of erythropoiesis. Red blood cells are involved in transporting oxygen and carbon dioxide.

• Small cells (7 to 8 µm diameter)
• Biconcave disc
• No nucleus
• Eosinophilic cytoplasm (bright pink) because of the high concentration of the protein hemoglobin

Mature red blood cells are released from bone marrow into the peripheral circulation. They circulate in blood for between 100 to 120 days.

Example:

• Red blood cells (60x)