von Willebrand factor is a large protein that plays a crucial role in blood clotting. It helps platelets, which are small cell fragments in the blood, stick to the walls of blood vessels when they are injured. This process is essential for forming a stable blood clot and preventing excessive bleeding. In addition to aiding platelet adhesion, von Willebrand factor also carries and protects another important clotting protein called factor VIII. When there is a deficiency or dysfunction of von Willebrand factor, it can lead to a bleeding disorder known as von Willebrand disease, which affects the body's ability to stop bleeding effectively.