Usually, every time you have a cut or bruise, your blood clots to stop the bleeding. Otherwise, you could bleed to death, even with a small cut.
Clotting is a complex process, and there are four main things that make it possible:
* Clotting factors, which are mostly special proteins
* Fibrin, which is a protein mesh, and finally
* Other cells, like red and white blood cells.
Because clot formation is SO important, platelets and clotting factors are always available, floating around in your blood. Many clotting factors are made in your liver with the help of vitamin K. Vitamin K is naturally found in foods such as leafy green vegetables and certain vegetable oils. This is important to remember later, when we talk about how Coumadin works, and why you have to be careful about your diet after you start taking it.
Now, let's talk about the four steps involved with forming a blood clot:
When there is a tear in a blood vessel, the first thing that happens is that the nearby platelets are activated and become sticky. They start sticking to each other and to the sides of the hole in the blood vessel. For small holes, enough platelets usually stick together to form a temporary plug. But a platelet plug isn't strong enough to block the opening for long, so it must be reinforced with other materials. Otherwise, the blood flowing past the hole could wash the plug away.
These other materials are called "clotting factors." As the clotting factors float by the tear, they become activated, or turned on, and some of them add themselves to the platelet plug. A special kind of clotting factor can weave itself together with others of the same kind and form a web of fibrous tissue, called fibrin. This web acts like glue and holds the platelets together, creating a blood clot.
Other cells, like red and white blood cells, can also get caught in this web, and help reinforce the clot. It quickly becomes stronger and starts to pull the edges of the hole in the blood vessel together. After the clot has formed, it stays in the hole until the tissue is repaired. When the clot is no longer needed, your body dissolves it.