hemostasiás

Hemostasia is the physiological process that stops bleeding. It is a complex and tightly regulated cascade involving blood vessels, platelets, and coagulation factors. When a blood vessel is injured, hemostasis is initiated to prevent excessive blood loss. The process can be broadly divided into several stages. First, vascular spasm occurs, where the injured blood vessel constricts to reduce blood flow. Second, platelet plug formation takes place. Platelets adhere to the damaged vessel wall and aggregate, forming a temporary plug. Third, coagulation, or blood clotting, is initiated. This involves a series of enzymatic reactions involving clotting factors in the blood plasma, ultimately leading to the formation of a fibrin clot. Fibrin is a protein that reinforces the platelet plug, creating a more stable and permanent seal. Finally, clot retraction and fibrinolysis occur. Clot retraction is the process by which the clot shrinks, further reducing the size of the wound. Fibrinolysis is the breakdown of the clot once the damaged vessel has been repaired. Disruptions in hemostasis can lead to either excessive bleeding (hemorrhage) or inappropriate clotting (thrombosis).