Blood clotting normally can be triggered by damage to a blood vessel. Platelets, tiny cells in the blood, immediately begin to adhere to the damaged part of the vessel and release chemicals to attract even more platelets. A platelet plug is formed, and the external bleeding stops.
Next, small molecules, called clotting factors, cause strands of blood-borne materials, called fibrin, to stick together and seal the inside of the wound. Eventually, the damaged blood vessel heals, and the blood clot dissolves after a few days.
