Trombotsitlar, beskvetli cella okrugloy, ovalnoy formy, razmerom 2-4 mk, kolichestvo v krovi 180-320 tys. v 1 mk, predstavlyayut soboy bezyadernye fragmenty citoplazmy, otdelivshiesya ot megakariotsitov, soderzhat spetsialnye granuly: faktor plastinok 4, faktor Vil'lebranda, tromboplastin, fibronektin i dr.