Hemostatic mechanisms showing the relationships among the vascular, platelet, and coagulation phases. Action is denoted by broken arrows, transformation by solid arrows. Circled factors are those that require vitamin K for activity. Proteins C and S, which degrade factors Va and VIIIa and require vitamin K for activity, are not shown. This figure is a highly simplified summary; see supplemental reading for further details. PL, platelet phospholipid; HMWK, high molecular weight kininogen; PreK, prekallikrein; ADP adenosine diphosphate; vWF, Von Willebrand factor; TxA2, thromboxane A2. (Modified with permission from Wintrobe MM et al. Clinical Hematology (7th ed.). Philadelphia: Lea & Febiger, 1974:390, 422.)
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