The wall that divides the right and left side of the heart isdiaphragmseptumpleurapericardium

The wall that divides the right and left side of the heart is called the septum.

Explanation:

The septum is a muscular wall that separates the right and left chambers of the heart, ensuring that oxygen-rich blood does not mix with oxygen-poor blood. It plays a crucial role in maintaining efficient circulation throughout the body. There are two parts to the septum: the interatrial septum, which divides the atria, and the interventricular septum, which separates the ventricles. This structural division is vital for the heart's functioning as it allows each side to operate effectively in its specific role in the circulatory system.

In summary, the correct answer to your question is septum.