The buffy coat over the volume of concentrated red blood contains white blood cells and platelets. Plasma has the largest percentage in the total blood volume. The kidney produces erythropoietin hormones which stimulate the production of red blood cells in the red bone marrow known as the process of erythropoiesis (Mader, 2010). Erythrocytes (red blood cells) essentially serve for the transport of oxygen and carbon dioxide for gas exchange. Red blood cells have no nucleus. They contain hemoglobin which binds mainly to oxygen to transport it to the tissues. Red blood cells have an average lifespan of 120 days and are destroyed by the spleen and liver. Degraded hemoglobin, iron and bilirubin are recycled. Nutrients such as vitamin B12, folic acid and iron are required for erythropoiesis. Leukocytes or white blood cells have a nucleus and are granular or agranular (Mader, 2010). Leukocytes are translucent and observed through staining. Granular leukocytes are neutrophils, basophils and eosinophils. Neutrophils are neutral or dyeless in color and have nuclei with more than 3 lobes (Sherwood, 2012). Eosinophils have the affinity of the red dye eosin while basophils have the affinity of the blue dye.