Monocytes exit the blood to become macrophages. They make up 2-6% of white blood cells and are phagocytic, defending against viruses and bacteria. Monocytes live for 10-20 hours in the blood and then become tissue macrophages in the tissues. Macrophages are important phagocytes that destroy invading bacteria and viruses through phagocytosis and by releasing oxidizing agents. They are found in tissues throughout the body, including the skin, lymph nodes, lungs, liver, spleen, and bone marrow, where they phagocytose foreign particles and pathogens.

1. 4. MONOCYTES * Exit blood (diapedesis) to become macrophages * 2-6 % of the WBC's * Phagocytic = defend against viruses and bacteria