normoblast

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(histology) The smallest of the nucleated precursors of the erythrocyte; slightly larger than a mature adult erythrocyte. Also known as acidophilic erythroblast; arthochromatic erythroblast; eosinophilic erythroblast; karyocyte; metakaryocyte; metanitricyte; metarubricyte.

A nucleated red blood cell found in the peripheral bloodstream in severe pernicious anemia and in some leukemias.

A nucleated red blood cell, the immediate precursor of a normal red blood cell in humans.

A nucleated precursor cell in the erythrocytic series; metarubricyte.
Four developmental stages are recognized: the pronormoblast (prorubricyte); the basophilic normoblast (basophilic rubricyte, erythroblast), in which the cytoplasm is basophilic, the nucleus is large with clumped chromatin, and the nucleoli have disappeared; the polychromatic normoblast (polychromatic erythroblast, rubricyte), in which the nuclear chromatin shows increased clumping and the cytoplasm begins to acquire hemoglobin and takes on an acidophilic tint; and the orthochromatic normoblast (acidophilic normoblast, metarubricyte, orthochromatic erythroblast), the final stage before nuclear loss, in which the nucleus is small and ultimately becomes a blue-black homogeneous structureless mass.

An erythroblast is a type of red blood cell which still retains a cell nucleus. It is the immediate precursor of a normal erythrocyte.

Nomenclature

The term normoblast is sometimes used as a synonym for erythroblast, but at other times it is considered a subcategory. In the latter context, there are two types of erythroblasts:

• "normoblasts" - develop as expected
• "megaloblasts" - an unusually large erythroblast that can be associated with pernicious anemia and folic acid deficiency (collectively called megaloblastic anemia)

Development

There are four stages in the development of a normoblast.

Image	Description
	Pronormoblast
	Basophilic normoblast
	Polychromatic normoblast (also polychromatophilic)
	Orthochromatic normoblast (also orthochromatophilic)

Additional images

Blood cell lineage

Hematopoiesis

See also

• Erythropoiesis
• Hemopoiesis
• Pluripotential hemopoietic stem cell

External links

• Pronormoblasts Presented by the University of Virginia
• Basophilic Normoblasts Presented by the University of Virginia
• Polychromatophilic Normoblasts Presented by the University of Virginia
• Orthochromatic Normoblasts Presented by the University of Virginia
• n_10/12578105 at Dorland's Medical Dictionary - "normoblast"
• e_15/12341680 at Dorland's Medical Dictionary - "erythroblast"
• normoblast at eMedicine Dictionary
• MeSH Normoblasts
• Histology at BU 01804loa - "Bone Marrow and Hemopoiesis bone marrow smear, erythroblast series with proerythroblast "
• Histology at uiowa.edu

Blood
General	Plasma - Hematopoietic stem cells
Lymphoid - WBC	T cells: Cytotoxic CD8+, Helper CD4+/Regulatory, γδ, Natural Killer T cell B cells: Plasma, Memory Natural killer cells (Lymphokine-activated killer cell)
Myeloid - WBC	Granulocytes (Neutrophil, Eosinophil, Basophil) - Mast cell precursors Dendritic cells (Langerhans cells, Follicular dendritic cells) Monocytes/Macrophages (Histiocytes, Kupffer cells, Langhans giant cells, Microglia, Osteoclasts) Megakaryoblast - Megakaryocyte - Platelets
Myeloid - RBC	Reticulocyte - Normoblast

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