Phagocytosis is the process in
cell biology in which a
cell engulfs a large particle, such as a
bacterium, by extending its
plasma membrane around it to form an internal
phagosome. It is a type of
endocytosis and is used both for feeding, especially by many
protists, and for defence in multicellular organisms. The phagosome may fuse with
lysosomes to form a
phagolysosome, where enzymes and antimicrobial chemicals break down the engulfed material. In the
immune system, phagocytosis is carried out by cells such as
neutrophils,
macrophages and
dendritic cells, which remove
pathogens, dead cells and debris. These cells are classed as
phagocytes. This video, captured through a
optical microscope and played back at eight times speed, shows a neutrophil in a drop of human blood engulfing a bacterium through phagocytosis.
Video credit: Andrei Savitsky
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