What Is a Clotting Mechanism?

The coagulation mechanism includes two aspects: coagulation and anticoagulation. The dynamic balance between the two is the key to the normal body to maintain blood flow in the body and prevent blood loss. The body's normal anticoagulation mainly depends on the complete structure and function of the blood vessel wall, effective platelet quality and quantity, and normal plasma coagulation factor activity.

Coagulation mechanism

The coagulation mechanism includes two aspects: coagulation and anticoagulation. The dynamic balance between the two is the key to the normal body to maintain blood flow in the body and prevent blood loss. The body's normal anticoagulation mainly depends on the complete structure and function of the blood vessel wall, effective platelet quality and quantity, and normal plasma coagulation factor activity.

After the human body is physically damaged, platelets will be stimulated by activating factors at the site of the injury, platelet aggregation will occur, and it will become a platelet clot, which plays a primary hemostatic role.

Platelets then undergo complex changes to produce thrombin, causing fibrinogen in the adjacent plasma to become fibrin, and intertwined fibrin entangles platelets with blood cells to form a blood clot, which is a thrombus (see clotting factors). At the same time, the protrusions of platelets extend into the fibrin network. The shrinkage of platelet microfilaments (actin) and myosin shrinks the blood clot, and the thrombus becomes firmer and can more effectively stop bleeding. This is secondary hemostasis. effect.

With the formation of thrombus, platelets release thromboxane A2; dense particles and alpha particles release ADP, serotonin, platelet factor 4, beta thromboglobulin, thrombin-sensitive protein,

Activation from factor X to fibrin formation is a common coagulation pathway for endogenous and exogenous coagulation. It mainly includes two stages of thrombin generation and fibrin formation.

Formation of thrombin:

That is, factor Xa and factor Va form a prothrombin complex, namely thromboplastin, in the presence of calcium ions and a phospholipid membrane, and convert prothrombin to thrombin.

Fibrin formation:

Fibrinogen is digested into fibrin monomers by thrombin and cross-linked to form a stable fibrin clot. This process can be divided into three stages: the generation of fibrin monomers, the polymerization of fibrin monomers, and fibers. Cross-linking of proteins. Fibrinogen contains three pairs of polypeptide chains, of which fibrin peptides A (FPA) and B (FPB) are more negatively charged. Thrombin hydrolyzes the more negatively charged fibrin peptides A and peptide B and removes them into fibers. Protein monomer. FPA and FPB released from fibrin molecules can reflect the degree of thrombin activation, so the determination of FPA and FPB concentrations can also be used to predict clinical hypercoagulability. After the fibrin monomers are generated, they are combined with non-covalent bonds to form fibrin polymers that are soluble in urea or chloroacetic acid, also known as soluble fibrin. After the formation of fibrin, it can promote the activation of factor XIII by thrombin. With the participation of XIIIa and calcium ion, adjacent fibrin undergoes rapid covalent cross-linking to form an insoluble stable fibrin clot. Fibrin has a high affinity for thrombin, so fibrin can adsorb thrombin after it is generated. This not only helps the formation of local blood clots, but also prevents thrombin from spreading into the circulation.