Pathology > Basic Hematology > Normal Hematopoiesis > RBC Basics: Maturational Morphology

RBC Basics: Maturational Morphology

Although most erythroid and myeloid cells decrease in size as they mature, the cytoplasm becomes relatively increased in volume, compared to the nucleus. The cytoplasm becomes less basophilic and increasingly eosinophilic.

Starting at the LEFT, CLICK on the above images to review RBC maturational morphology.

The pronormoblast (E1) is the earilest recognizable red cell precursor. They are 15- 20µ in diameter with fine granular chromatin and 0-2 nucleoli. The cytoplasm is deeply basophilic without granules.

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The chromatin is slightly coarser and the cell slightly smaller than the pronormoblast. Nucleoli may be indistinct. The cytoplasm remains deeply basophilic.

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The chromatin becomes increasingly coarse compared to the E2 stage. The cytoplasm remains basophilic, but has a lighter tinctorial quality than E2.

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Hemoglobin production becomes evident from the muddy mix of the blue staining RNA and the red staining hemoglobin resulting in the greyish cytoplasm of the E4 polychromatophilic normoblast. The chromatin is moderately condensed.What is the cell to the right of the arrow?

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The E5 orthochromatic normoblast is smaller than the E4 stage. In the E5 orthochromatic normoblast hemoglobin is abundant while ribosomes decrease in number. The nuclear chromatin is pyknotic and ready to be extruded.

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Polychromatophilic red cells are larger than mature erythrocytes and still contain ribosomes and mitochondria, giving the cell a blue tint. When polychromatic RBCs are stained with a supravital dye (new methylene blue or cresyl violet) ribosomes clump to form a blue stained granulars called reticulum. These are called reticulocytes.

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Normal mature erythrocytes are biconcave discs (approximately 8 um in diameter; 2.5 um thick at the periphery; 1.0 um thick at the center). This results in an area of central pallor (about 1/3 the dia.) seen in mature RBCs stained with Wright's-Giemsa.

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Why does the cytoplasm become more eosinophilic as RBCs mature?

How do reticulocytes differ from mature erythrocytes?

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