Atrioventricular septum

The atrioventricular septum is a septum of the heart between the right atrium (RA) and the left ventricle (LV).

Although the name "atrioventricular septum" implies any septum between an atrium and a ventricle, in practice the divisions from RA to RV and from LA to LV are mediated by valves, not by septa. Also, there is usually no communication between the LA and the RV.