text: The spleen is the largest lymphoid organ in the body but has other functions. It breaks down both red and white blood cells that are spent. This is why it is sometimes known as the graveyard of red blood cells. A product of this digestion is the pigment bilirubin, which is sent to the liver and secreted in the bile. Another product is iron, which is used in the formation of new blood cells in the bone marrow. Medicine treats the spleen solely as belonging to the lymphatic system, though it is acknowledged that the full range of its important functions is not yet understood.