Which of the following cells or blood elements play a role in the initial phases of wound healing?

a. Polymorphonuclear leukocytes (PMNs)

b. Platelets

c. Monocytes

d. Lymphocytes

Shortly after the initial injury, the wound is full of debris which is cleared over the next several days by recruited and activated phagocytic cells. PMNs begin to arrive immediately, reaching large numbers within 24 hours. The PMNs are followed by macrophages which appear in wounds in significant numbers within two to three days. Macrophages are mononuclear phagocytic cells derived from circulating monocytes or resident tissue macrophages. They complete the process of removing all material not necessary for the ensuing steps of wound healing. Lymphocytes also appear in wounds in small numbers during the inflammatory response. The role of lymphocytes in the wound healing process remains to be clarified, but they are thought to be more related to the chronic inflammatory processes than the initial response to wounding. Platelets are anuclear discoid blood elements derived from bone marrow megakarocytes which play a role in the initial hemostatic process as well as releasing chemotactic factors and factors leading to fibroblast proliferation.