The traditional picture does not help in understanding cardiac physiology.
The cutaway heart does not help either.
It is important to unravel the heart and its vasculature.
And then, line the heart up in a unidirectional flow :
In a nutshell : the pulmonary circuit (vasculature) is shown in the diagram above.
Blood has to traverse the route of : RA > RV > pulmonary circuit > RA > RV (and then out the Aorta).