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How do white blood cells move from the blood to sites of infection in body tissues?
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white blood cell
Blood is made up of multiple components, including red blood cells, white blood cells, platelets, and water-rich plasma.
White blood cells (leukocytes) reach sites of infection or tissue injury by migrating from the bloodstream into body tissues. This process involves several key mechanisms:
- Chemotaxis: White blood cells, such as neutrophils, are guided to specific locations by chemical signals released at sites of tissue damage or infection. This force of attraction, known as chemotaxis, determines the direction of their movement.1
- Margination: Within blood vessels, many white blood cells move slowly along the inner walls (the marginal pool), positioning themselves to exit the circulation upon receiving a chemotactic signal.1
- Diapedesis: Once signaled, these cells pass through the walls of capillaries and venules to enter the surrounding tissues. This passage of blood cells through vessel walls is called diapedesis.23
- Amoeboid Motion: Once outside the blood vessels, cells like neutrophils move through the tissues using amoeboid motion, extending projections called pseudopodia to advance toward the site of infection.1
Once they arrive, these cells perform vital defensive functions, such as phagocytosis to ingest and destroy pathogens.241