Heme is conveed to bilirubin mainly in

Heme is conveed to bilirubin by the macrophages of reticuloendothelial system. (Mainly in the spleen, but also in the liver and bone marrow). The tissue macrophage system includes the following phagocytic cells: * In bone marrow - lining of blood sinuses (littoral cells) * In liver - intervals along vascular capillaries (Kupffer cells) * In spleen - in the pulp * In lymph nodes - line the lymphatic paths The destruction of RBCs occur mostly in the capillaries of spleen as they have very thin lumen. Because of this, spleen is called the graveyard of RBCs.