phagocytózis

Phagocytosis is a cellular process whereby a cell engulfs large particles. The name comes from the Greek words "phagein" meaning "to eat" and "kytos" meaning "cell". This is a form of endocytosis, where the cell membrane invaginizes to surround and internalize material from the extracellular environment. The internalized substance is then enclosed within a membrane-bound vesicle called a phagosome.

Phagocytosis is primarily carried out by specialized cells known as phagocytes. These include certain types of white blood cells in animals, such as macrophages, neutrophils, and dendritic cells. In unicellular organisms like amoebas, phagocytosis is a primary mechanism for obtaining nutrients. The process is crucial for immune defense, where phagocytes engulf and destroy invading microorganisms like bacteria and viruses, as well as cellular debris and dead or dying host cells.

Once the phagosome is formed, it fuses with lysosomes, which are organelles containing digestive enzymes. This fusion creates a phagolysosome, where the engulfed material is broken down and eliminated. The ability of phagocytes to engulf and clear foreign particles and cellular waste is essential for maintaining tissue homeostasis and protecting the organism from disease.