Nucleated red blood cell in the normal development of a normoblast. A megaloblast is an unusually large erythroblast that can be associated with vitamin B deficiency (caused by pernicious anemia or dietary insufficiency), folic acid deficiency, or both (such anemias are collectively called megaloblastic anemias). This kind of anemia leads to macrocytes (abnormally large red cells) and the condition called macrocytosis. The cause of this cellular gigantism is an impairment in DNA replication that delays nuclear maturation and cell division. Because RNA and cytoplasmic elements are synthesized at a constant rate despite the cells' impaired DNA synthesis, the cells show nuclear-cytoplasmic asynchrony. NRB's can
White blood cell ways. Two pairs of broadest categories classify them either by structure (granulocytes or agranulocytes) or by cell lineage (myeloid cells or lymphoid cells). These broadest categories can be further divided into the five main types: neutrophils, eosinophils (acidophiles), basophils, lymphocytes, and monocytes. These types are distinguished by their physical and functional characteristics. Monocytes and neutrophils are phagocytic. Further subtypes can be classified; for example, among lymphocytes, there are B cells, T cells, and NK cells. The number of leukocytes in the blood is often an indicator of disease, and thus the "white blood cell count" is an important subset of