In humans red blood cells are primarily produced in the red marrow, to which body system does the red marrow belong to?

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.