What is the thick muscular wall between the two ventricles called?

The thick muscular wall between the two ventricles of the heart is called the interventricular septum. It separates the left and right ventricles, preventing the mixing of oxygenated and deoxygenated blood. This structure is crucial for the efficient functioning of the heart, as it helps maintain the pressure needed for blood to be pumped effectively to the lungs and the rest of the body.