Blood clotting

1. Occurs when a blood vessel breaks from an injury.

1.1. Platelets stick to the broken vessel wall and clump together, blocking the cut. Fibrinogen is converted to a protein called fibrin (enzyme called thrombin), which forms a mesh of fibrin fibres across the wound. More platelets stick to the mesh and form a scab to prevent bleeding by blocking the cut.

1.2. Blood loss is prevented and the vessel heals, which also prevents pathogens from entering the blood vessel.