Alveolar macrophage phagocytosis of E. coli (mammal lung pleural cavity), coloured scanning electron micrograph (SEM). Note the macrophage has short filopodia that extend from the cell and aid in finding bacteria for phagocytosis. A tissue macrophage is a large, mature phagocyte that can ingest and destroy invading microbes, foreign particles, cancerous or diseased cells and cellular debris. Alveolar (lung pleural cavity) macrophages are part of the reticuloendothelial system. Magnification: x925 when shortest axis printed at 25 millimetres.