The interventricular septum is a thick wall of muscle that separates the left and right ventricles of the heart. This structure plays a crucial role in maintaining the heart's efficiency by preventing the mixing of oxygen-rich blood from the left ventricle with oxygen-poor blood from the right ventricle. Made up of both muscular and fibrous tissue, the interventricular septum also helps support the heart's shape and function. It is essential for proper blood circulation, as it allows the ventricles to contract effectively during each heartbeat, contributing to the overall performance of the cardiovascular system.