phagocytosis (Alternative spelling: phagocytosis) is a form of endocytosis and refers to the uptake of small (food) particles by a cell. The term derives from the ancient Greek word 'phagein' (to eat). If a cell takes up liquid from the extracellular space instead of solids, it is called pinocytosis.
The phagocytosis can i.a. observed in some species of unicellular organisms, including e.g. Amoebae, flagellates and cilia. It can be deduced from this that phagocytosis - evolutionarily considered - already established itself very early as ability for food intake.
Phagocytes (phagocytes) play an important role in the human body. As a component of the immune system or immune defense, macrophages eat pathogens that have invaded the body after immune cells recognize and mark them as foreign. In addition, phagocytes also eat the body's own cells, which were stimulated to apoptosis due to irreversible cell defects.

Simplified course of phagocytosis

1. The inclusion of the non-cellular particle takes place. The particle is first enclosed and pinched off to a vesicle (phagosome). The phagosome is now in the cell body of the phagocyte.
2. One or more lysosomes fuse with the phagosome, causing the contents of the lysosomes (digestive enzymes) to come into contact with the particle.
3. The digestive enzymes (lipases, proteases, nucleases) split the particle into smaller units. This degradation process is enhanced by the acidic pH of the lysosomal cytosol.
4. The vesicle with the now released particle, fuses with the membrane of the macrophage and releases the now harmless individual components to the outside. The phagocyte can now pick up the next particle.