Red blood cells are commonly referred to as erythrocytes; they are non-nucleated cells elements in the blood. The red color of red blood cells is caused by the presence of hemoglobin; they are larger in number compared to other blood cells.
Normal red blood cell is disk-shaped and biconcave. The normal red blood cell count in humans is 4 -5.5vmillon /cu mm of blood; the diameter is 7.2micro. Surface area 120 sq μ, volume 85 to 90 cu μ. Normal Red blood cells are not nucleated. Nucleated RBC is mostly found in camels and dogs but not a healthy human. The most common nucleated red blood cells are fully hemoglobinized or orthochromatic. These are usually immature RBC. The increase of nucleated red blood cells referred to normoblasts.