The right atrium (RA) and right ventricle (RV) are opened.
You can see the tip of a needle (*) that crosses the membranous septum from the left ventricle. The right bundle branch is clearly seen (arrow). Dissection technique: naked eye in formolized heart.
References:
1= thebesian veins
2= foramen ovale
3= Tricuspid Valve
4= muscle of Lancici
5= orifice of the SCV
6= orifice of the ICV
7= tuber of Lower

Image #37