White blood cell White blood cell White blood cells (also called leukocytes or leucocytes and abbreviated as WBCs) are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from multipotent cells in the bone marrow known as hematopoietic stem cells. Leukocytes are found throughout the body, including the blood and lymphatic system. All white blood cells have nuclei, which distinguishes them from the other blood cells, the anucleated red blood cells (RBCs) and platelets. Types of white blood cells can be classified in standard
Blood cell are based on the inappropriate production of white blood cells. Platelets, or "thrombocytes", are very small, irregularly shaped clear cell fragments, 2–3 µm in diameter, which derive from fragmentation of megakaryocytes. The average lifespan of a platelet is normally just 5 to 9 days. Platelets are a natural source of growth factors. They circulate in the blood of mammals and are involved in hemostasis, leading to the formation of blood clots. Platelets release thread-like fibers to form these clots. If the number of platelets is too low, excessive bleeding can occur. However, if the number of platelets is too high,