piastrine

Piastrine, or platelets, are small, anucleate cell fragments circulating in the blood. They are produced by megakaryocytes in the bone marrow and typically measure about 2–3 micrometers in diameter. Platelets play a central role in hemostasis, the process that stops bleeding.

In response to vascular injury, platelets adhere to exposed subendothelial structures, particularly to von Willebrand factor, via surface receptors such as GPIb-IX-V. They become activated, release inflammatory and pro-aggregatory mediators, and recruit additional platelets. Through interactions involving the GPIIb/IIIa receptor and fibrinogen, platelets aggregate to form a primary hemostatic plug. Platelets also provide a procoagulant surface that supports thrombin generation, reinforcing clot formation and stabilization.

Platelet production, or thrombopoiesis, is regulated mainly by thrombopoietin. Platelets have a lifespan of about 7–10 days and are removed primarily by the spleen and liver.

Normal platelet count is typically between 150 and 450 x 10^9/L. Abnormal platelet numbers or function can lead to clinical disorders: thrombocytopenia (low platelets) increases bleeding risk and can result from decreased production, increased destruction, or sequestration; thrombocytosis (high platelets) can be linked to increased thrombotic risk. Platelet disorders can be quantitative or qualitative (impaired function) and are evaluated with complete blood counts and specialized tests.

Therapeutically, antiplatelet drugs reduce platelet function to prevent thrombosis, while platelet transfusions may be used to treat significant bleeding or prepare patients for surgery.