In the clotting process, as the hemostatic plug develops, fibrin polymerizes into monomeric threads which are held together by noncovalent bonds. Which clotting protein increases the strength of the clot by crosslinking the newly formed fibrin threads?
Fibrinogen is cleaved by thrombin twice as it is activated to form fibrin. The initial cleavage causes it to polymerize and the second causes it to branch. Thrombin also activates Factor XIII to XIIIa, which crosslinks the fibrin strands and strengthens the clot. HMWK is a cofactor in the intrinsic pathway that conves Factor XI to XIa. Plasminogen is a central proenzyme in clot lysis. When plasminogen is conveed to plasmin, it digests fibrin threads, as well as a number of protein factors including Factors V, VIII, XII, and prothrombin. Thrombin is an enzyme derived from prothrombin. It conves fibrinogen to fibrin, and activates factor XIII. vWF is a tissue-bound protein which is exposed with vascular trauma and helps in the process of platelet adhesion.
Factor XIII
High molecular weight kininogen (HMWK)
Plasminogen
von Willebrand Factor (vWF)