Final answer:
White blood cells perform phagocytosis to defend against pathogens, with neutrophils specifically engulfing and digesting invaders like bacteria at the site of infection.
Step-by-step explanation:
White blood cells, also known as leukocytes, are a crucial part of the immune system. They defend the body against invading pathogens through a process known as phagocytosis. This process involves the white blood cell surrounding and engulfing the bacteria, or other pathogens. Neutrophils, a type of white blood cell, are particularly adept at this task. Once engulfed, the pathogen is contained within a phagosome, which then fuses with a lysosome, leading to the digestion and destruction of the pathogen.
Another aspect of the immune response is the movement of white blood cells from the bloodstream to the site of infection, a process called extravasation or transendothelial migration. Here, the cells leave the bloodstream and migrate towards the site of inflammation to target the pathogens directly.