Phagocytosis    

Phagocytosis is the ingestion of huge particles like as bacteria and cell debris through large endocytic vesicles known as phagosomes.In order to be ingested the particle must first bind to the surface of the phagocyte, commonly by specialized cell surface receptors. Once it is bound to the receptors, the phagocyte is stimulated   to start   engulfing   the particle   with   its plasma   membrane,   thus enclosing it within a phagosome shown in the figure.  The phagosome then fuses with a lysosome    and the ingested particle is broken down.  The Utilizable material will be transported into the cytosol, although indigestible substances will remain in the lysosomes building residual bodies. In protozoa, phagocytosis is a form of feeding whereas the ingested material is broken down in the lysosomes and utilized as food. In the multicellular organisms only a few specialized cells are capable of phagocytosis.  Neutrophils and Macrophages (white blood cells) use phagocytosis to protect the organism against infection through ingesting invading microorganisms. The Macrophages   are   also   included in scavenging damaged and dead cells and cell debris.