| Definition |
The cellular components of blood include erythrocytes (red blood cells), leukocytes (white blood cells), and platelets. Normal human blood contains 4.8 - 5.2 million erythrocytes/ml and 4000 - 10,000 leukocytes/ml. Leukocytes are divided into five classes based on morphological and tinctorial characteristics when stained, all of which are involved in the body´s defense systems. The five classes of leukocytes are: neutrophils (40% - 75%), eosinophils (1% - 6%), basophils (less than 1%), monocytes (2%-10%), lymphocytes (20%-45%). Collectively, neutrophils, eosinophils, and basophils are known as granulocytes due to the presence of granules in their cytoplasm. In addition, monocytes and lymphocytes are also known as mononuclear cells.
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