due to the presence of the muscle valve in the right atrioventricular orifice in the bird heart , the `` '' extension '' '' of the pacemaker area of the atrioventricular node and a respective obvious branching of the purkinje fibers of the atrioventricular bundle seem to take place .
C0034144
e purkinje fibe
C0006382
atrioventricular bund