Red bone marrow is responsible for Hematopoiesis.

Hematopoiesis is important to our body because it provides us new blood cells (RBC, WBC and Platelet) everyday. It is the formation of new blood cells by means of Hematopoietic stem cells (HSCs) or hemocytoblasts.

Hematopoietic stem cells (HSCs) or hemocytoblasts are the Stem cells of blood cells. In developing embryos, blood formation occurs in aggregates of blood cells in the yolk sac, called blood islands. As development progresses, blood formation occurs in the spleen, liver and lymph nodes. When bone marrow develops, it eventually assumes the task of forming most of the blood cells for the entire organism. However, maturation, activation, and some proliferation of lymphoid cells occurs in secondary lymphoid organs (spleen, thymus, and lymph nodes). In children, hematopoiesis occurs in the marrow of the long bones such as the femur and tibia. In adults, it occurs mainly in the pelvis, cranium, vertebrae, and sternum. That’s why Skeletal and Circulatory Systems are realated.