leukocyte
Leukocyte refers to the cells in the blood other than red blood cells. When blood is centrifuged, white blood cells form a white layer of 'buffy coat' between the plasma layer and the red blood cell layer, and the color of this layer is called white blood cell because it is white. Normal adults have about 4.5 to 11.0 × 109 per liter of blood, and this number is significantly smaller than that of red blood cells. Like erythrocytes, they are produced in the bone marrow, and their lifespan varies depending on the type of white blood cell. Unlike erythrocytes, leukocytes are classified into various types of granulocytes and granulocytic leukocytes, depending on the presence of specific granules in the cytoplasm. Granulocytic leukocytes have eosinophils, basophils, neutrophils, and granulocytic leukocytes have lymphocytes and monocytes. The proportion of neutrophils is 54 ~ 62%, followed by lymphocytes 25 ~ 45%, monocytes 4 ~ 8%, and eosinophils and basophils 5%.