Blood Platelets, Thrombocytes

Platelets are cells of the blood, and represent a functional element of the endogenous blood clotting.

Due to their disintegration as a result of mechanical irritation, prothrombin activators are released which activate the conversion of prothrombin into thrombin. Through the action of thrombin, monomeric fibrin molecules are formed from fibrinogen, which then polymerize. In addition, calcium ions and factor XIII are involved in the formation and stabilisation of the cross-linked fibrin clot.

https://en.wikipedia.org/wiki/Platelet _([1])