normoblast

normoblast /nor·mo·blast/ (nor´mo-blast)

1. orthochromatic erythroblast.

2. term now often used as a synonym of erythroblast; sometimes more specifically, a nucleated cell in the normal course of erythrocyte maturation, as opposed to a megaloblast. When used in the latter sense, the four developmental stages of the nucleated cells of the erythrocytic series are usually named pronormoblasts (proerythroblasts) and basophilic, polychromatophilic, and orthochromatic normoblasts (see under erythroblast). normoblas´tic

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nor·mo·blast (nôrm-blst)

n.

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

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normoblast (nôr´mōblast),

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

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normoblast

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.