Final answer:
The process by which white blood cells (leukocytes) leave the bloodstream to enter body tissues is known as emigration or diapedesis. This movement allows leukocytes to perform their immune functions at injury or infection sites.
Step-by-step explanation:
The process by which cells leave the peripheral bloodstream is called emigration or diapedesis. Leukocytes, or white blood cells, utilize this method to exit the capillaries and enter body tissues. This event is crucial for the immune response, allowing leukocytes to reach sites of infection or injury where they may be renamed based on their function, such as macrophage or microglia.
During diapedesis, leukocytes squeeze between the cells of blood vessel walls, leaving the circulatory system to fight pathogens. This process is distinct from the movement of an embolus—a thrombus that has broken free and entered circulation. Diapedesis is essential for maintaining the body's defense mechanisms, and it showcases the unique ability of leukocytes to respond to the body's needs.