What is the physiological function of platelets?

As we all know, platelets are a substance in the blood. The so-called leukemia in daily life is related to platelets. The main problem is that there is a problem with the coagulation mechanism. If there are no platelets, it will be difficult to stop bleeding once our body starts bleeding. If I were to describe it, platelets are like our glue. So, from a scientific point of view, what are the physiological functions of platelets?

Platelets are small pieces of cytoplasm that detach from the cytoplasm of mature megakaryocytes in the bone marrow. Although megakaryocytes are the smallest in number among the hematopoietic cells in the bone marrow, accounting for only 0.05% of the total number of bone marrow nucleated cells, the platelets they produce are extremely important for the body's hemostatic function. When blood is lost due to vascular trauma, the functional activities of platelets in the physiological hemostasis process can be roughly divided into two stages: the first stage is mainly after the trauma occurs, platelets quickly adhere to the trauma site, aggregate into clusters, and form a relatively soft hemostatic plug; the second stage is mainly to promote blood coagulation and form a solid hemostatic plug.

Three major physiological functions of platelets

1. Vasoconstriction: The vascular endothelium is damaged, platelets adhere to the subendothelial tissue and release vasoconstrictor substances such as 5-hydroxytryptamine and TXA2, causing vasoconstriction.

2. Platelet thrombosis

(1) Platelet adhesion identifies the site of injury and allows the hemostatic plug to be correctly positioned.

(2) Activated platelets release ADP and TXA, which promote irreversible platelet aggregation and form platelet thrombus, achieving initial hemostasis.

3. Blood coagulation

(1) Activated platelets provide a phospholipid surface for the activation of coagulation factors during blood coagulation, and participate in the activation of coagulation factor X and prothrombin in the intrinsic and extrinsic coagulation pathways. Platelets also release coagulation factors such as fibrinogen, which greatly accelerates the coagulation process.

(2) The platelets in the blood clot contract, causing the blood clot to retract and squeeze out the serum, making the blood clot more solid and firmly sealing the damaged part of the blood vessel.