Awesome Anatomy

White blood cells, or leukocytes, are cells in human blood (and also in the lymphatic system, spleen, and other tissues) that are produced in bone marrow and are critical to the proper function of the immune system. A healthy human has between 7000 and 25,000 white blood cells per drop of blood; a human with leukemia has up to 50,000 white blood cells per drop.


There are several types of white blood cells, but the most common are neutrophil granulocytes, eosinophil granulocytes, basophil granulocytes, monocytes, macrophages, and granulocytes. All granulocytes engulf invaders of different sorts and digest them. Neutrophils attack bacteria, basophils release histamine (thus being complicit in allergies), and eosinophils attack parasites. Lymphocytes include killer T cells, and are found primarily in the lymphatic system; these and other lymphocytes destroy infected human cells. Monocytes enable T cells to recognize their viral targets; these cells are critical in developing immunities. When monocytes are found in human tissue, they are called macrophages.


A number of diseases can strike white blood cells, the most outstanding of which is leukemia. Leukopenia is the opposite, in which there is a deficit of white blood cells.