The wounding event leads to damage of blood vessels, which initiates a clotting cascade involving complement factors in the blood, ultimately leading to the formation of fibrin clots. This blocks pathogens from accessing the blood or tissues at the injury site. Vasoconstriction occurs to aid the biochemical cascade and cause hypoxia, which attracts white blood cells into the tissue and causes a humoral and cellular inflammatory response. This occurs extremely quickly and leads to the release of vasoactive factors like histamine and bradykinin, which maintain the flow of blood factors to deal with the damaged tissue and any pathogens at the wound site. This allows wound exudates to seep through to the damaged area carrying inflammatory immune factors for repair.
Plasma factors including lysozyme, white blood cells and macrophages then begin the process of removing dead cells and debris from the tissue. These cells are important for directing the healing process through cytokines and growth factors.
Hemostasis is a general term given to the process which aims to stop the bleeding and thus prevent significant loss of blood, and to close the wound and block the entry of pathogens as quickly as possible. Central to hemostasis is the clotting process; denatured polymers such as collagen and other foreign bodies in the injured site activate substances known as complement factors in the blood; these act on a soluble, blood-borne thrombin precursor (prothrombin) to cause it to change to thrombin. Thrombin brings about the cleavage of the protein fibrinogen to form an insoluble fibrin clot; fibrin is then further cross-linked by an enzyme in blood called Factor XIII. The cascade of events also results in the release of vasoactive factors to accelerate blood clotting.
The extent of the clotting process, the biochemical makeup of the hemostasis cascade, and the density of the fibrin clot are dictated by a combination of genetic and environmental factors. It is thought that the clotting process has evolved, over many millennia of evolutionary development, to be very efficient at stopping bleeding rapidly, preventing infection, and stimulating repair, at some cost in terms of the resultant cosmetic appearance of the healed skin.
Products, technologies, companies and markets in the field of hemostasis are covered in the 2010 MedMarket Diligence report #S180, "Worldwide Surgical Sealants, Glues, Wound Closure and Anti-Adhesion Markets, 2008-2015."