There are four major phases of response to injury: inflammatory, proliferative, contraction, and remodelling.

INFLAMMATORY PHASE

After injury, prostaglandins are released in conjuction with vascular constriction, followed by vasodilation. A hemostatic plug is formed by the platets attatching to the exposed collagen. Other substances released during this stage include adenosine diphosphate, growth factors, clotting factors, and vasoactive substances, such as histamine. A fibrin network is formed when coagulation occurs. The site of injury is protected from bacteria initially by enzymes released by platelets.

After six hours Polymorphonuclear lymphocytes (PMNs) appear and phagocytize bacteria and other foreign bodies. Then T and B cells appear after the PMNs. White blood cells, (T and B cells) enter the wound after the PMNs and their numbers peak at 6 days after injury. T cells secrete substances called lymphokines. Helper-T cells are also a significant component of wound healing.Within two to three days after injury macrophages enter the wound and may remain at the injury site for many weeks.