What is coagulation?

Coagulation is the means by which we stop bleeding (hemostasis) and form blood clots after injury to blood vessels. Essentially, coagulation is the coagulation of blood, an extremely important process. The way our bodies clot blood has been a subject of intensive study, as some people with certain diseases such as hemophilia are unable to do so. Understanding when clotting is more harmful than harmful, such as when a blood clot causes a stroke, has increased our understanding of the value of this process and when it might need to be stopped.

You can describe coagulation in the simplest terms as a multipart system that is initiated by damage to a blood vessel. The first thing that happens during coagulation is constriction . The constriction shrinks the injured blood vessel, causing it to move blood at a much slower rate. This translates to less bleeding.

Second, platelets, an important part of the blood, come together at the site of injury to form a platelet plug . These platelets tend to be signaled by a release of proteins that signal the forward march for platelets to congregate at the site of injury. However, the platelet plug is only a temporary form of clotting. More is needed to keep the platelet plug in place.

The body has proteins , more than 20 types, which are then moved to the site of injury to help strengthen the platelet plug. One final protein, thrombin , forms a mesh-like protection for the platelet plug, essentially ending the clotting process. This mesh is called fibrin mesh and acts as a booster for the platelets, holding them in place and ultimately keeping the blood clotted.

The fibrin mesh actually gets stronger as the wound ages, usually healing the wound completely. Wound scabs, for example, are part blood, part platelets, and part fibrin mesh. Proteins that help the blood clot interact with the air when the wound is external, helping to harden and strengthen a scab. After the coagulation process is over, the scab will gradually become useless and fall off. Picking the scab can restart coagulation if the blood vessels are not completely healed.

We know a lot about clotting because the presence of too many platelets or too many certain types of proteins can cause blood clots to form when they shouldn't. In some cases, narrowed arteries can cause platelets to stick together and clot, resulting in a stroke. When people undergo heart surgery, the danger of blood clotting is high, and people are often given drugs called anticoagulants to prevent blood from clotting quickly. They work throughout the body, and people who take them can have a stopped clotting process when they get hurt or cut.

Other people lack some of the proteins needed for the body to complete the clotting process. The absence of these proteins can be extremely dangerous and even minor injuries can lead to significant blood loss. People may also lack adequate numbers of platelets, which is a condition called thrombocytopenia . This may be temporary and can occur when people undergo cancer treatment. Occasionally, the coagulation process is significantly affected by anticoagulants such as warfarin and heparin, and the result is induced thrombocytopenia. Again, this poses a great risk to the person with the condition, but can be corrected with platelet transfusions.

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