Next, activated factor XI (XIa) catalyzes the conversion of factor IX into IXa in the presence of ionized Calcium. Then activated factor IX (IXa), along with ionized calcium, platelet factor, and factor VIII, activates factor X, which activates the next factor, prothrombin into thrombin in the common pathway.
The activation of factor X signals the beginning of the common pathway.
The activated partial thromboplastin time (aPTT) monitors the intrinsic pathway and the effectiveness of heparin therapy.
