Interventricular septum

The interventricular septum (IVS) (or ventricular septum), which develops from the fetal septum inferius, is the stout wall separating the lower chambers (the ventricles) of the heart from one another.

The interventricular septum is directed obliquely backward to the right, and curved toward the right ventricle. Its margins correspond with the anterior and posterior interventricular sulci.

Most of the interventricular septum is thick and muscular. This part is called the muscular interventricular septum. The superior and posterior part of the interventricular septum, separating the aortic vestibule from the lower part of the right atrium and upper part of the right ventricle, is thin and fibrous. This part is called the membranous interventricular septum (septum membranaceum).