hemostázist

Hemostasis is the physiological process by which bleeding is stopped. It is a crucial mechanism that prevents excessive blood loss following injury to blood vessels. The process involves a complex series of events that can be broadly divided into primary and secondary hemostasis.

Primary hemostasis begins immediately after a blood vessel is damaged. This involves the constriction of the injured vessel, a process called vasoconstriction, which reduces blood flow. Simultaneously, platelets in the blood adhere to the site of injury and aggregate, forming a temporary plug. This platelet plug is the initial barrier against further bleeding.

Secondary hemostasis follows primary hemostasis and involves the coagulation cascade. This is a complex enzymatic pathway involving a series of clotting factors, proteins circulating in the blood. The cascade ultimately leads to the formation of fibrin, a protein that reinforces the platelet plug, creating a stable clot. This fibrin mesh traps blood cells and further seals the injured vessel.

Once the bleeding is controlled and the vessel wall has been repaired, a process called fibrinolysis begins. This is the breakdown of the blood clot by enzymes, primarily plasmin, which dissolves the fibrin and restores normal blood flow. Hemostasis is a finely tuned process, and its dysregulation can lead to either excessive bleeding (hemorrhage) or abnormal clot formation (thrombosis).