The movement of blood through the heart?

OK

DE-OXYGENATED blood enters the right atrium via the superior and inferior vena cava

it the passes through a cardiac valve into the right ventricle then into the pulmonary artery to the lungs . The de-oxygenated blood passes to the aveolia(small air sacs in lungs) via a network of capillaries. Diffusion occurs and an exchange of gases take place (co2 goes into the aveolia ready to be breathed out and the oxygen from breathing in that is stored in the aveolia goes into the blood. The blood is now oxygenated!

Now the oxygenated blood goes into left atrium via pulmonary veins, through another valve into the left ventricle and then up to the Aorta carrying oxygenated blood to the rest of the body and back to the vena cavas.

I hope that helped :)