Coagulation refers to the process of blood changing from a flowing liquid state to a non-flowing gel state. Its essence is the process of soluble fibrinogen in plasma changing to insoluble fibrin. This process is an important physiological mechanism of the human body, which helps to prevent excessive blood loss after vascular injury.
The details are as follows:

Coagulation Process

Vasoconstriction

When the vascular wall is damaged, the vascular smooth muscle will immediately contract, making the vascular diameter smaller and the blood flow slower to reduce bleeding.

Platelet aggregation

Collagen fibers exposed at the site of vascular injury will activate platelets, causing them to adhere to the site of injury and release a variety of bioactive substances, such as adenosine diphosphate (ADP), thromboxane A₂ (TXA₂), etc. These substances further induce platelet aggregation, forming platelet thrombi and temporarily blocking the wound.

Coagulation factor activation

At the same time as platelet thrombi are formed, coagulation factors in plasma are activated, initiating a series of complex coagulation cascade reactions. These coagulation factors usually exist in the plasma in an inactive form. When they receive activation signals, they will be activated in turn to form prothrombin activators. Prothrombin activators convert prothrombin into thrombin, and thrombin then cuts fibrinogen into fibrin monomers. Fibrin monomers are connected to form fibrin polymers, and finally form a solid blood clot.

Physiological Significance of Coagulation

Coagulation is an important mechanism for the human body to protect itself. It can quickly form blood clots when blood vessels are damaged, effectively preventing blood from continuing to flow out, and avoiding shock or even death due to excessive blood loss. At the same time, the coagulation process also provides a stable environment for wound healing, which is conducive to tissue repair and regeneration.

Abnormal Coagulation

Abnormal coagulation function, whether it is too strong or too weak, will cause harm to human health. If the coagulation function is too strong, blood clots may easily form in the blood vessels, blocking the blood vessels and leading to serious diseases such as myocardial infarction and stroke; if the coagulation function is too weak, bleeding may not stop after a minor trauma. For example, hemophilia patients lack certain coagulation factors in their bodies, so a minor collision or injury may cause severe bleeding.