Definition of Cardiac septum

Cardiac septum: The dividing wall between the right and left sides of the heart. That portion of the septum that separates the two upper chambers (the right and left atria) of the heart is termed the atrial (or interatrial) septum; the portion that lies between the two lower chambers (the right and left ventricles) of the heart is called the ventricular (or interventricular) septum.

Source: MedTerms™ Medical Dictionary
http://www.medterms.com/script/main/art.asp?articlekey=9120
Last Editorial Review: 3/19/2012