What is the structure that separates the right and left sides of the heart?

The Septum is a partition that separates the right and left sides of the Heart. There are two separate regions of the Septum. They are the Interatrial Septum that separates the Atriums and the Interventrial Septurm that separates the Ventricles. The Interatrial Septum is only present in the fetal period and is open during this period. The Interatrial Septum closes at the time of birth. The Interventrial Septum is suppose to be closed all the time but sometimes an opening is present at birth. This would be considered a Congenital Heart disease.