Blood clotting normally occurs when there is damage to a blood vessel. Platelets immediately begin to adhere to the cut edges 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 cut blood vessel heals and the blood clot dissolves after a few days.
Update Date 6/22/2015
Updated by: Denis Hadjiliadis, MD, MHS, Associate Professor of Medicine, Pulmonary, Allergy, and Critical Care, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.