The depiction of an event late in the game was inspired by Crisis Core: Final Fantasy VII, a storyline tying into the opening of Final Fantasy VII. Ifrit's throne resembles the throne Chaos sits in in a concept art piece by Yoshitaka Amano. for the original Final Fantasy.
The blood first enters the heart into the right atrium. Blood passes from the right atrium through the tricuspid valve and into the right ventricle. When the right ventricle contracts, the muscular force pushes blood through the pulmonary semilunar valve into the pulmonary artery. The blood then travels to the lungs, where it receives oxygen. Next, it drains out of the lungs via the pulmonary veins, and travels to the left atrium.
Blood enters the lungs via the pulmonary arteries. It then proceeds through arterioles and into the very tiny alveolar capillaries. Oxygen and carbon dioxide are exchanged between the blood and the air; oxygen is loaded onto the red blood cells while carbon dioxide is unloaded from them into the air. The oxygenated blood then flows out of the alveolar capillaries, through venules, and back to the heart via the pulmonary veins.