Okay, I just wrote on the previous post if you had learnt about how the heart works?
I figured the question out and I'm another another lesson :p
Alright... In case you don't know the heart is decided into 4 regions we call chambers. So using that picture you have try to portion it out into four parts. Of course right and left are completely swapped when it comes to the heart as you can see from my diagram. So just remember that the right atrium has the superior and inferior cavas that are the large trucks that take back deoxygenated blood back to the heart from upper and lover parts of the body. |dw:1434118017933:dw| Blood starts of being deoxygenated, coming from the rest of the body i.e the systemic circulation, and enters the left atrium, J . (See my diagram and try to compare it with your image). Blood then goes through the tricuspid valve, which is in between both the right atrium and ventricle (H) . Blood then flows into the right ventricle where it contacts and blood is delivered to the pulmonary trunk (it also goes through the pulmonary semilunar valve K. In your picture this is structure B. From their the blood is supplied to the lung by right and left pulmonary arteries and then the lungs. Here gas exchange occurs. (Not really shown in your image but good to know this :) ) Blood then, when it is oxygenated goes into the heart through two pairs of pulmonary veins, each leaving the lung. It then enters the left atrium, and passes through the bicuspid valve, E and into the left ventricle F. The ventricle having lots of myocardium contracts and pushes the blood into the aorta (B) where it exits the heart and is pumped out into the rest of the cardiovascular system. The valve D is the aortic semilunar valve.