Editing Coagulation (section)

====Tissue factor pathway (extrinsic)====
{{Anchor|Extrinsic pathway}}
The main role of the [[tissue factor]] (TF) pathway is to generate a "thrombin burst", a process by which [[thrombin]], the most important constituent of the coagulation cascade in terms of its feedback activation roles, is released very rapidly. FVIIa circulates in a higher amount than any other activated coagulation factor. The process includes the following steps:<ref name="Pallister1" />

# Following damage to the blood vessel, FVII leaves the circulation and comes into contact with tissue factor expressed on tissue-factor-bearing cells ([[stromal cell|stroma]]l fibroblasts and leukocytes), forming an activated complex (TF-FVIIa).
# TF-FVIIa activates FIX and FX.
# FVII is itself activated by thrombin, FXIa, FXII, and FXa.
# The activation of FX (to form FXa) by TF-FVIIa is almost immediately inhibited by [[tissue factor pathway inhibitor]] (TFPI).
# FXa and its co-factor FVa form the [[prothrombinase]] complex, which activates [[prothrombin]] to thrombin.
# Thrombin then activates other components of the coagulation cascade, including FV and FVIII (which forms a complex with FIX), and activates and releases FVIII from being bound to vWF.
# FVIIIa is the co-factor of FIXa, and together they form the "[[tenase]]" complex, which activates FX; and so the cycle continues. ("Tenase" is a contraction of "ten" and the suffix "-ase" used for enzymes.)