Red Blood Cell Terminologies

Erythrocyte Development

• RBCs are formally called erythrocytes
• Nucleated precursors in the bone marrow are called erythroblasts

Pronormoblast/Rubriblast/Proerythroblast

• Largest of the erythroid precursors
• Nucleus:
  • N:C ratio: 4:1
  • Chromatin: fine and dark staining
  • Nucleoli: 1-2
• Cytoplasm:
  • Heterogeneous
  • Dark blue (distinctly basophilic)
  • No granules

Prorubicyte/Basophilic Normoblast (Erythroblast)

• Nucleus:
  • N:C ratio: 4:1
  • Chromatin: partially clumped, wheel with broad spokes
  • Nucleoli: ABSENT
• Cytoplasm:
  • Deeply basophilic
  • No granules

Rubicyte/Polychromatic Normoblast (Erythroblast)

• "Dawn of hemoglobinization"
• Last stage capable of mitosis
• Nucleus:
  • N:C ratio: 1:1
  • Chromatin: increasingly clumped
  • Nucleoli: ABSENT
• Cytoplasm:
  • Mixtures of red-staining hemoglobin with blue RNA in varying shades of gray
  • Pink coloration mixed with basophilia → Muddy, light gray appearance

Metarubicyte/Orthochromic Normoblast (Erythroblast)

• Nucleated RBC
• Mitosis no longer possible
• Nucleus:
  • N:C ratio: LOW
  • Chromatin: pyknotic (dense or compact)
  • Nucleoli: ABSENT
• Cytoplasm:
  • Acidophilic (reddish pink) cytoplasm
  • Salmon-pink color

Polychromatic Erythrocyte

• Called reticulocytes when stained with a vital stain
• No nucleus
• Polychromatophilic due to retention of RNA
• Synthesizing hemoglobin for 2-3 days in the marrow and for 1 day in the blood
• Seen in Wright's stain as large bluish-red cells, Polychromatophilic macrocytes

Erythrocyte

• No nucleus
• Biconcave disc
• Salmon pink-staining cell with a central pale area
• Area of central pallor of 1-3 um (1/3 of the cell)
• Circulate for about 120 days