What anatomical feature separates the two sides of the heart?

The septum is the anatomical feature that separates the two sides of the heart, specifically dividing the right and left atria from each other and the right and left ventricles. This muscular wall plays a crucial role in ensuring that oxygenated and deoxygenated blood do not mix, thus maintaining the efficiency of the heart's function. The right side of the heart receives deoxygenated blood from the body and pumps it to the lungs for oxygenation, while the left side receives oxygenated blood from the lungs and pumps it to the rest of the body.

Valves, although essential for regulating blood flow in the heart and preventing backflow, do not separate the heart into right and left sections. The aorta is the major artery that carries oxygenated blood away from the heart, but it is not involved in the division of the heart itself. The pericardium is a protective sac surrounding the heart that provides cushioning but does not function as a divider between the heart's chambers.