hæmostasis

Hemostasis is the physiological process that stops bleeding. It is a complex, tightly regulated series of events involving blood vessels, platelets, and plasma proteins. When a blood vessel is injured, hemostasis is initiated to prevent excessive blood loss and maintain blood pressure.

The process begins with vascular spasm, where the smooth muscle in the wall of the injured blood vessel constricts, reducing blood flow. This is followed by platelet plug formation. Platelets, small blood cells, adhere to the site of injury and aggregate, forming a temporary plug.

The final and most crucial stage is coagulation, also known as blood clotting. This involves a cascade of reactions involving numerous clotting factors in the plasma. These factors ultimately lead to the formation of fibrin, a protein that forms a meshwork, reinforcing the platelet plug and creating a stable blood clot.

Once the bleeding is controlled and tissue repair begins, the clot is gradually broken down by a process called fibrinolysis, which removes the clot and restores normal blood flow. Disorders of hemostasis can lead to either excessive bleeding (hemorrhage) or inappropriate clotting (thrombosis).