You are in the kitchen chopping some vegetables when you accidentally cut yourself. You wash the
wound with water, and it stops bleeding within a few minutes. This is because the blood has formed a clot which is helping the bleeding to stop.
Ever wonder how blood actually clots?
The human blood is made of millions of cells, each serving a different function. Amongst these cells are platelets - a type of cell that is responsible for the clotting of blood. There are number of different steps involved in blood clotting. Below is a brief description of what really happens.
1. The blood vessel sustains a cut or injury. This injury sends out signals to the platelets, which rush to the site of injury to start the healing process. The platelets clump together and form a 'platelet plug' that plugs the hole through which the bleeding is taking place.
2. A chemical reaction begins which stimulates proteins in the blood (released from the liver) called clotting factors. These are called factors V, VII, IX and X (Roman numerals). The clotting factors are responsible for the formation of fibrin, which are protein strands that help provide strength and stability to the platelet plug.
3. Since clotting is a chemical process, there must be something to keep it under check so that blood does not continue to clot. These are 'clotting police', and include factors called protein C, protein S and similar proteins. They ensure that clotting only occurs where injury has taken place and not anywhere else in the body.
Over time, the blood clot becomes harder and is eventually broken down and disappears. This is brought around by an enzyme called plasmin.
The entire clotting process takes around 2 to 6 minutes. Cool, right?!
But there is a dark side to clotting.
Blood clotting is a protective process, but is the cause of conditions such as stroke and heart attacks. For example, in a heart attack, the narrowed blood vessels that night have formed from atherosclerosis lead to turbulent flow, causing damage to the blood vessel lining. This triggers the platelets in the blood stream to form platelet clumps, evenutally leading to blood clot formation.
The blood clot blocks off the blood vessel, depriving the heart muscle of nourshing oxygen rich blood. This leads to a heart attack. A similar phenomenon occurs in the brain as well, leading to strokes. It is not uncommon for this to happen in the legs as well, leading to an 'ischemic' limb. This can lead to gangrene, and sometimes may need amputation.
Blood thinners such as Aspirin, Clopidogrel and Warfarin are required to prevent this process in such situations. They are life saving treatments and may be needed long term.