Coming through the tricuspid AV valve, we enter into the larger-sized right ventricle. I hope you brought everything with you because looking back at that valve you'll see that it's closed and won't let us back through to the atrium. It's the same with all the valves in the heart. The plan is to always have everyone moving in the one direction only, so a fully functional heart stops anyone from going back to where they just came from.
As you have a look around, you'll notice that the muscle walls here are thicker than in the right atrium. The atria only need to send us into the next room, but the ventricles needs to push us a further distance.
