The interventricular septum is the muscular partition which divides and isolates the right ventricle from the left ventricle. It is an inner projection of the myocardium that separates both lower cavities of the heart. It is formed by three muscular layers of both ventricles. It is almost as thick as the wall of the left ventricle and it slightly bulges into the right ventricle.
The upper portion of the interventricular septum is thin and it is called the membranous part. The septal cusp of the tricuspid valve is attached to it. The bundle of Hiss travels through it, dividing in two as the septum becomes thicker. On the left and right side, this dividing wall is covered by the endocardium.
Below, schematic image of the human heart, exhibiting the interventricular septum.
