Final answer:
Leukocytosis involves the mobilization of leukocytes, including granulocytes and monocytes, from the bone marrow to an injury site in response to chemical signals, to perform defense functions such as the destruction of pathogens and phagocytosis.
Step-by-step explanation:
Leukocytosis is the release of leukocytes from the bone marrow to the injury site. Leukocytes, or white blood cells, are essential for the body's immune response and are produced in the bone marrow. When an injury or infection occurs, these cells are mobilized to the site of damage or infection. Leukocytes respond to chemical signals and are attracted to the area through a process known as chemotaxis. In this process, injured or infected cells release chemical signals that serve as a "chemical 911 call" to attract leukocytes for defense and repair. Key players in this response include granulocytes such as neutrophils and eosinophils, which can release chemicals to destroy pathogens and perform phagocytosis, and monocytes, which can differentiate into macrophages that also phagocytize pathogens and assist in tissue healing.