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Phagocytosis means cell-eating. It is the process the body uses to ingest and digest infectious agents, such as bacteria, and also cell debris, such as worn-out cells.
Phagocytosis is carried out by 2 main types of white blood cells: macrophages and neutrophils (collectively called phagocytes).
Macrophages and neutrophils are attracted out of the bloodstream to a site of inflammation in the body by chemicals that are released when micro-organisms, such as bacteria, damage the body’s tissues.
The first stage of phagocytosis is when phagocytes attach to the bacterium or substance to be eaten. Then the macrophage extends tentacles called pseudopods around the bacterium. The pseudopods enclose the bacterium forming a phagosome.
The macrophage has several enclosed packets of digestive enzymes within it. These are called lysosomes.
The phagosome moves deeper into the cell and fuses with one of the lysosomes, forming a phagolysosome. The phagolysosome contains hydrogen peroxide, free radicals and digestive enzymes. The contents of the phagolysosome are digested and the phagolysosome moves towards the surface of the macrophage. The wastes are released to the outside of the macrophage.
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2. Iles RK. Cell and molecular biology, and genetic disorders. In: Kumar P, Clark M, editors. Clinical Medicine (5th Edition). London: WB Saunders; 2002. p. 154-55.
3. Merck Manuals Online Medical Library [website]. Biology of the immune system (updated 2008, Sep). Available at: http://merck-ut.merck.com/mmpe/print/sec13/ch163/ch163a.html (accessed 2010, Jun 22)