Erythrocyte

Erythrocyte (Mature Erythrocyte)

• Bone marrow : 0 %
• Peripheral blood : Predominant cell type
• Size : 7-8 μm
• No nucleus
• No nucleoli
• No chromatin 
• No N/C ratio 
• Cytoplasm: Salmon with central pallor of about one-third of the diameter of the cell

NOTE: The mature erythrocyte has lost the blue-gray color and is salmon colored as hemoglobinization is complete. 

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Reticulocyte

Reticulocyte ( Polychromatic Erythrocyte / Diffusely Basophilic Erythrocyte )

• Size = 7-10 μm
• No nucleus (so there is no N/C ratio)
• No nucleoli
• No chromatin
• Cytoplasm: Color is slightly more blue/purple than the mature erythrocyte because there are RNA remnants.
• Bone marrow: 1 %
• Peripheral blood: 0.5 - 2.0 % 

NOTE:  When stained with supravital stain (e.g., new methylene blue), polychromatic erythrocytes appear as reticulocytes (contain precipitated ribosomal material)

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Orthochromic Normoblast

Orthochromic Normoblast ( Orthochromic Erythroblast / Metarubricyte )

• 1 - 4% of nucleated cells in BM
• Peripheral blood: 0 %
• Size = 10 -15 μm
• Low N/C ratio (1:2)
• Round nucleus
• No nucleoli
• Fully condensed chromatin 
• Cytoplasm: more pink or salmon than blue 

NOTE: The gray-blue color of the cytoplasm is becoming salmon as more hemoglobin is produced. 

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Polychromatophilic Normoblast

Polychromatophilic Normoblast ( Polychromatic Normoblast / Polychromatic Erythroblast / Rubricyte )

• 13-30% of nucleated cells in BM.
• Peripheral Blood : 0 % 
• Size = 12 - 15 μm
• Low N/C ratio (4:1)
• Eccentric nucleus
• No nucleoli 
• Chromatin irregular and coarsely clumped
• Cytoplasm: Gray-blue as a result of hemoglobinization 

NOTE: The blue color of the cytoplasm is becoming gray-blue as hemoglobin is produced. 

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Basophilic Normoblast

Basophilic Normoblast (Basophilic Erythroblast / Prorubricyte)

• 1-3% of nucleated cells in BM.
• Peripheral blood : 0 %
• Size = 16-18 μm
• Round to slightly oval nucleus
• Moderate N/C ratio (6:1) 
• Dark blue cytoplasm
• Indistinct nucleoli ( 0 - 1 nucleoli ) 
• Coarsening ( slightly condensed ) chromatin

 

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Pronormoblast

Pronormoblast (also known as Proerythroblast / Rubriblast) is the first microscopically recognizable cell in erythrocyte lineage.

• 1% of Nucleated Cells in BM.
• Peripheral Blood: 0%
• 1% of Nucleated Cells in BM.
• Size: 20-25 μm
• Nucleus: Round to slightly oval
• High N/C ratio (8:1)
• 1-3 faint nucleoli 
• Fine chromatin
• Cytoplasm: Dark blue; may have prominent Golgi

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Morphologic Characteristics of Erythroid Precursors

Pronormoblast (rubriblast):

• 1% of Nucleated Cells in BM.
• Size = 20-25 μm.
• High N/C ratio (8:1)
• 1-3 faint nucleoli 
• Lacy chromatin 

Basophilic normoblast (prorubricyte):

• 1-3% of nucleated cells in BM.
• Size = 16-18 μm
• Moderate N/C ratio (6:1)
• Indistinct nucleoli
• coarsening chromatin

Polychromatophilic normoblast (rubricyte):

• 13-30% of nucleated cells in BM.
•  Size = 12 - 15 μm
• Low N/C ratio (4:1)
• Chromatin irregular and coarsely clumped
• Eccentric nucleus

Orthochromic normoblast (metarubricyte):

• 1-4% of nucleated cells in BM
• Size = 10 -15 μm
• Low N/C ratio (1:2)

Reticulocyte (new methylene blue stain):

• Size = 7-10 μm
• No N/C ratio because there is no nucleus

Reticulocyte (Wright’s stain):

• Polychromatophilic (diffusely basophilic)

Mature RBC:

• Size = 7 -8 μm
• No nucleus

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