Macrophage is-

The monocytes migrate to tissues and become part of the tissue (fixed) macrophages. Blood macrophages → Monocytes Tissue macrophages → Histiocytes Tissue macrophages (histiocytes) in different tissue are mentioned below – Lung: ‘Alveolar macrophages’ or ‘Dust’ cells Placenta: Hoffbauer cells Brain: Microglia Kidney: Mesangial cells Liver: Kupffer cells Spleen: Littoral cells Bone: Osteoclasts Synovium: Type-A lining cells Skin: Langerhans cells Spleen: Red pulp sinusoidal lining cells Connective tissue: Histiocytes (tissue macrophages) Lifespan of monocytes in circulation is 1-3 days whereas tissue macrophages have life span of 3 months to years