Coagulation, or thrombogenesis, is the process by which blood clots in an attempt to restrict blood loss from an injury site, and repair the damaged vessel. Most of the time clotting is a good thing, however there are circumstances when a clot can form abnormally, leading to heart attack, stroke, or other serious medical problems. A blood clot forms almost immediately after the bleeding occurs, which is possible through enzymes and other substances in blood that respond to breaks in vessel walls. The clot is a temporary fix preventing further blood loss. There are four major parts of blood clot formation. The first step in clotting is the formation of the platelet plug. Platelets are the smallest of the three major types of blood cells whose primary function is to prevent bleeding.
When encountering a damaged blood vessel, the platelets become stimulated and rush to the injury site where they clump together, forming a plug and restricting the bleeding. They also release substances to begin the chemical reaction of the clotting process. These chemical reactions are responsible for growing the blood clot. Dissolved proteins, also referred to as clotting factors, are contained within the blood for the purpose of promoting blood clots. These proteins send signals to each other and enhance each other’s activity exponentially at the site of injury, resulting in a rapid chemical chain reaction which produces fibrin, the main protein forming clots. This blood clot formed with fibrin is tougher and more durable than the platelet plug.
Once the blood clot forms, it is important that it not grow and spread to the rest of the body, which can cause serious damage. This is where “anti-clotting” comes in to play. Proteins such as antithrombin, protein C, and protein S, are known anti-clotting proteins and exist in a natural balance with the clotting factors. These substances work to neutralize excess clotting factors, preventing the clot from going to places it should not. The final part of the process is where the clot is slowly broken down by the body. Once the damaged tissue heals, the body gradually degrades the clot and reabsorbs it. The tough fibrin strands in a blood clot are dissolved by an enzyme called plasmin. Plasmin is activated by other substances working together to help the clot break down.
The whole process of blood clotting is whenever the blood is exposed to certain substances. These are known as thrombogenic substances because they promote the formation of thrombus (clot). Many of these substances, such as tissue factor, collagen, and von Willebrand factor, are located in the skin or in the blood vessel walls, typically separated from flowing blood. If they come into contact with flowing blood, this typically means the blood vessel wall is ruptured and bleeding. A clot may also form when blood is not flowing properly. http://www.hematology.org/patients/blood-disorders/blood-clots/5233.aspx http://www.webmd.com/a-to-z-guides/blood-clots