Phagocytosis ('cell eating') is the process of engulfing and destroying extracellularly-derived material by a phagocytic cell, such as a macrophage, neutrophil, or amoeba. It is a form of endocytosis. In it, the cell changes shape by sending out projections called pseudopodia.
The phagocytic cell may be attracted to a particle like a bacteria or virus by a chemical attractant – a process known as chemotaxis. The phagocytic cell sends out membrane projections that make contact with the target particle. A receptor ligand interaction occurs between the phagocytic cell surface and the particle that will be ingested. Pseudopodia then surround the particle and, when the cell membrane of the projection meet, membrane fusion occurs. This results in the formation of a large intracellular vesicle. Lysosomes then merge with the vacuole, turning it into a digestive chamber. Finally, the products of the digestion are released into the cytosol.