Blood clotting, also known as coagulation, is a vital process that prevents excessive bleeding when a blood vessel is injured. It involves a complex cascade of events: 1. Vasoconstriction: Immediately after injury, the blood vessel constricts to reduce blood flow. 2. Platelet Plug Formation: Platelets in the blood adhere to the site of injury and aggregate, forming a temporary plug. 3. Coagulation Cascade: A series of protein interactions (clotting factors) is activated. This cascade ultimately leads to the conversion of fibrinogen, a soluble protein, into fibrin, an insoluble protein. 4. Fibrin Clot Formation: Fibrin strands form a meshwork that traps blood cells and platelets, reinforcing the platelet plug and forming a stable clot. 5. Clot Retraction and Dissolution: Over time, the clot retracts, pulling the edges of the injured vessel together. Eventually, an enzyme called plasmin breaks down the clot.