An organ consisting of the right atrium, right ventricle, left atrium, and left ventricle. Non-oxygenated blood enters the heart through the precava and postcava (large veins from the rest of the body) and oxygenated blood leaves through the aorta. Pulmonary arteries and veins carry the blood over the lungs in order for it to become oxygenated and recycled through the body.

If you have ever held a heart in your hand (the closest I have ever come is a cat's heart during Biology class), you will know that it is a beautiful, perfect, powerful thing.