Now let's move on to stage number two. In stage number two, the right atrium is now fully filled with our de oxygenated blood, and the left atrium is also filled with our oxygenated blood. And this causes the two atrium to contract. And when they contract, they open up the tricuspid valve and they also open up our bicuspid, or mitral valve. So let's begin with the right pump. So the right atrium is fully filled with the deoxynative blood and it contracts and enforces the opening of our tricuspid valve.