fagocytosis

Phagocytosis is a cellular process by which certain types of cells engulf and internalize large particles, such as microorganisms, cellular debris, and foreign substances. This essential function is primarily carried out by specialized cells called phagocytes, which are a type of white blood cell. The term "phagocytosis" is derived from the Greek words "phagein" meaning "to eat" and "kytos" meaning "cell."

The process begins when a phagocyte recognizes a target particle, often signaled by specific molecules on its surface. The phagocyte then extends projections of its cell membrane, called pseudopods, to surround and enclose the particle. This engulfment results in the formation of a membrane-bound vesicle within the phagocyte, known as a phagosome.

Once the phagosome is formed, it fuses with lysosomes, which are organelles containing powerful digestive enzymes and toxic molecules. This fusion creates a phagolysosome, where the enclosed material is broken down and neutralized. The resulting waste products are then either expelled from the cell or recycled for other cellular functions.

Phagocytosis plays a crucial role in the immune system, where it helps to clear pathogens and remove damaged or dead cells, thereby preventing inflammation and infection. It is also involved in tissue remodeling and development. Cells that perform phagocytosis include macrophages, neutrophils, and dendritic cells.