Bone marrow is the site of hematopoiesis, that is, generation of all blood cells including erythrocytes, lymphocytes and platelets from common pluripotent hematopoietic stem cell. Hematopoietic stem cell generates two types of multipotent progenitor cells, one that generates lymphoid and the other that generates erythrocytes and platelets. At birth, hematopoiesis takes place in bones throughout the skeleton, but as an individual ages, it shifts and becomes restricted to bone marrow of flat bones such as sternum, vertebrae, iliac bones and ribs. In case of injury or extreme production of new blood cells occurs, liver and spleen become the sites of hematopoiesis. Cytokines simulate the proliferation and maturation of precursor cells in the
