Physiological hemostasis process

Some girls will have irregular menstruation after their period. At this time, their period will not go away for a long time. This situation will cause certain harm to women. Although bleeding during menstruation is the shedding of the inner wall of the uterus, it will not really lose blood in the female body, but it will also cause women's qi and blood to be weak, so it is necessary to stop bleeding when necessary. So what is the process of physiological hemostasis?

1. The process of physiological hemostasis

The process of physiological hemostasis mainly includes three processes: vasoconstriction, platelet thrombus formation and blood coagulation.

1. Vasoconstriction

Physiological hemostasis first manifests itself as contraction of the damaged blood vessel and nearby small blood vessels, resulting in a reduction in local blood flow.

The mechanisms include: reflex vasoconstriction caused by damaging stimulation, myogenic contraction of local blood vessels caused by vascular wall damage, and the release of vasoconstrictor substances such as 5-HT and TXA2 by platelets adhered to the injured area.

2. Platelet thrombosis

The subendothelial collagen is exposed, and a small number of platelets adhere to the subendothelial collagen. The adhered platelets further activate the signaling pathway within the platelets, leading to platelet aggregation.

The release of ADP by locally damaged red blood cells and the thrombin generated during local coagulation can both activate platelets and release endogenous ADP and TXA2, thereby activating and recruiting more platelets to form a platelet hemostatic plug to block the wound and achieve initial hemostasis, which is called primary hemostasis.

3. Blood coagulation

After a blood vessel is damaged, coagulation factors are activated in a certain order to generate thrombin, which eventually converts the soluble fibrinogen in the plasma into insoluble fibrin, which are interwoven into a network to strengthen the hemostatic plug, which is called secondary hemostasis.

It includes three basic steps: prothrombin complex formation, thrombin activation and fibrin generation.

2. Coagulation Process

1. Formation of the prothrombinase complex

(1) Intrinsic coagulation pathway

It refers to the process in which all factors involved in coagulation come from the blood and the coagulation process is usually initiated by the contact of blood with the negatively charged surface of a foreign object.

FXII + foreign body surface → FXIIa → XIa + Ca2+ → FIXa +

Ca2+ + FVIIIa → Factor X enzyme complex → FXa.

FVIII and vWF in plasma are non-covalently combined to form a complex, which improves its stability and prevents FVIII from being degraded by activated protein C. Therefore, vWF deficiency in von Willebrand disease will lead to a decrease in FVIII.

APTT (activated partial thromboplastin time) is a relatively sensitive and most common screening test for the intrinsic coagulation system. Prolonged APTT is common in factors XII, XI, IX, VIII, X, V, II, PK (prokallikrein), HMWK (high molecular weight kininogen) and fibrinogen deficiencies, such as hemophilia (factor VIII/IX deficiency).