FXIIa plays {HEAD ~ a very important role} in the initiation stage in the intrinsic blood clotting system, fibrinolysis system and {TAIL ~ plasma kallikrein kinin system} 
FXIIa plays { HEAD ~ a very important role } in the initiation stage in the intrinsic blood clotting system , fibrinolysis system and { TAIL ~ plasma kallikrein kinin system }
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL