Red bone marrow belongs to the lymphatic system. While it is housed within bone all lymphocytes develop in bone marrow as well as use it as a conduit for the cells to begin circulation. Hematopoieses happens here were marrow-derived stem cells differentiate (choose what they will become) into either fully mature cells of the immune system or precursors ( will change later) that travel out of the bone marrow. Bone marrow produces: B cells, natural killer cells, granulocytes and immature thymoctyes, red blood cells and platelets.