Nucleated red blood cell Nucleated red blood cell All vertebrate organisms have hemoglobin-containing cells in their blood and with the exception of mammals, all of these red blood cells contain a nucleus. Mammals represent ~5,500 named species out of ~66,000 vertebrate species, and within this ~8% subgroup, red blood cells are known as erythrocytes or RBCs and lack a cell nucleus in mature organisms. In contrast, a nucleated red blood cell (NRBC), also known by several other names, is a mammalian RBC that contains a cell nucleus. NRBCs occur in normal development as progenitor cells in the erythropoietic lineage and in pathological states. Normally,
Red blood cell synthesised by the kidney. Just before and after leaving the bone marrow, the developing cells are known as reticulocytes; these constitute about 1% of circulating red blood cells. The functional lifetime of a red blood cell is about 100–120 days, during which time the red blood cells are continually moved by the blood flow push (in arteries), pull (in veins) and a combination of the two as they squeeze through microvessels such as capillaries. They are also recycled in the bone marrow. The aging red blood cell undergoes changes in its plasma membrane, making it susceptible to selective recognition by