Factor IXa then combines with factor VIIIa and procoagulant phospholipid (present on the surface of activated platelets, endothelial cells, and tissue cells) to form a complex that activates factor X. In the extrinsic pathway, factor VIIa and tissue factor (TF) directly activate factor X (and, perhaps, also factor IX —see figure Pathways in blood coagulation and table Components of Blood Coagulation Reactions).