What Is the Clotting Process?

Blood coagulation is a process in which thrombin generated by the corresponding activation of coagulation factors in a certain order finally makes fibrinogen into fibrin.

Coagulation process

Blood coagulation is a process in which coagulation factors are activated in a certain order, and finally fibrinogen is converted into fibrin, which can be divided into: formation of thrombin activator;

Formation of prothrombin activator

Prothrombin activators are Xa, V, Ca2 +, and PF3 (platelet factor 3, a phospholipid on the platelet membrane) complex. The formation of prothrombin activator requires the activation of factor x. According to the different initiation pathways and participation factors of prothrombin activator formation, coagulation can be divided into two pathways: endogenous coagulation and exogenous coagulation.
(1) endogenous coagulation pathway: activated by factor activation. When the blood vessels are damaged and the subintimal collagen fibers are exposed, it can activate to a, which in turn activates to a. a activates a in the presence of Ca2 +, and a forms a complex with activated a, PF3, and Ca2 + to further activate X. The factors involved in the coagulation of the above processes are all present in the blood plasma, so they are named endogenous coagulation pathway. Due to the presence of factor VIIa, it can accelerate the activation of X by 200,000 times. Therefore, the lack of factor IX causes endogenous coagulation pathway disorders, and minor injuries can cause more than bleeding. It is clinically called hemophilia A.
(2) Exogenous coagulation pathway: It is initiated by the exposure of factor of the damaged tissue to the blood. When the tissue is damaged and the blood vessel is ruptured, the exposed factor III forms a complex with Ca2 + and in the plasma to activate factor X. Because factor III, which initiates this process, comes from extravascular tissues, it is called the exogenous coagulation pathway.

Thrombin formation

Under the action of prothrombin activator, inactive factor II (prothrombin) in plasma is activated into active factor IIa, (thrombin).

Fibrin formation

Under the action of thrombin, fibrinogen dissolved in plasma is transformed into fibrin monomers; at the same time, thrombin activates XIII to XIIIa, which connects fibrin monomers to each other to form a water-insoluble fibrin polymer, and Intertwined with each other, the blood cells are trapped inside, forming a blood clot, and completing the blood clotting process.
Blood coagulation is a series of enzymatic biochemical reaction processes. There are positive feedback effects in many places. Once started, it will continue quickly to ensure that the hemostatic effect of coagulation occurs in a short time.