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White blood cells or leukocytes are cells which form a component of the blood. They are produced in the bone marrow and help to defend the body against infectious disease and foreign materials as part of the immune system. There are normally between 4x109 and 11x109 white blood cells in a litre of healthy adult blood — about 7,000 to 25,000 white blood cells per drop. In conditions such as leukaemia this may rise to as many as 50,000 white blood cells in a single drop of blood. As well as in the blood, white cells are also found in large numbers in the lymphatic system, the spleen, and in other body tissues.
Nomenclature The name "white cells" derives from the fact that after centrifugation of a blood sample, the white cells are found in the Buffy coat, a thin layer of nucleated cells between the sedimented red blood cells and the blood plasma, which is white in color (or sometimes green, if there are large amounts of neutrophils in the sample, which are high in green myeloperoxidase).A drop of blood can contain from anywhere from 7000 to 25000 white blood cells Types There are many different types of white blood cells. One primary technique to classify them is to look for the presence of granules, which produces the categories "granulocytes" and "agranulocytes". These categories can be further broken down as follows: Diseases Other tissue cells See also | ||||||||
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