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