1

BLOOD COAGULATION CASCADE

• .Intrinsic pathwayBlood disturbances and platelet phospholipids activate factor XII to initiate the intrinsic coagulation pathway, which leads to the activation of (factor X).X

Extrinsic pathwayWhen a vessel is injured, (tissue factor, or thromboplastin) is released from the endothelium initiating the extrinsic coagulation pathway, which leads to the activation of (factor X).

TF

X

Common pathway (factor II, or prothrombin) is converted by factor Xa into factor IIa, or thrombin.

Thrombin cleaves (factor I, or fibrinogen) to form fibrin (factor Ia), a key component of clot formation.

II

I

Adapted from Ansell J. J Thromb Haemost. 2007;5(suppl1):60-64.Guyton AC, Hall JE. Hemostasis and blood coagulation. In: Textbook of Medical Physiology. 10th ed. Philadelphia, PA: WB Saunders Co; 2000:419-429.Moake JL. Hemostasis. In: Porter RS, Kaplan JL, Homeier BP, eds. The Merck Manual Online. http://www.merck.com/mmpe/sec11/ch134/ch134a.html. Accessed March 4, 2008.

Fibrin Clot

Xll

Xl

lX

VIIIa VII

TF

Va

II

I

X

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