atrioventricular septum

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

The septum primum will continue to grow until the sixth week when the dorsal and ventral cushions will fuse to form the atrioventricular septum.

The atrial canal is in turn divided into a right and left side by the atrioventricular septum, which originates from the union of the dorsal and ventral endocardial cushion.

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.