The anterior descending artery (yellow arrows) bring the first septal and also a second of the same diameter (another variety). The very first supplies the zone of the crista supraventricularis and the bundle zone.
Look at the pulmonary valve (Pv) and its proximity with the first septal (marked with a silver bead).
1: right ventricular aspect of the ventricular septum.
Lv: left ventricle
Tv: tricuspid valve
Mb: moderator band
Pv: pulmonary valve.