What occurs during emigration?

• A. Antibodies cross endothelium
• B. Lymphocytes mature in thymus
• C. Phagocytes attach to the endothelial lining and migrate to surrounding tissues
• D. White blood cells leave the bone marrow

Answer: (C)

Emigration is the movement of white blood cells from the bloodstream into tissues where they're needed, a process also called diapedesis. During this step, phagocytes such as neutrophils and monocytes adhere to the endothelial lining, squeeze through gaps between endothelial cells, and then migrate toward chemical signals at the site of infection or injury. That description matches the idea of phagocytes attaching to the endothelium and migrating into surrounding tissues.

The other scenarios describe different processes: antibodies crossing the endothelium is a transport event, not emigration; maturation of lymphocytes in the thymus is development of T cells; and white blood cells leaving the bone marrow refers to hematopoiesis or egress into the blood, not migration from blood into tissue.