What is the ventricular septum?

• A. A membranous structure between ventricle and atrium
• B. Wall between atria
• C. Common muscular wall between left and right ventricles
• D. A layer of pericardium

Answer: (C)

The ventricular septum is the wall that separates the left and right ventricles. It is primarily muscular, forming a thick barrier that keeps oxygen-rich blood in the left ventricle from mixing with the deoxygenated blood in the right ventricle. A small membranous portion exists near the top, but the main structure is muscular. This separation also provides a path for part of the heart’s electrical conduction system, helping coordinate ventricular contraction. The other descriptions refer to different structures: a membranous part between ventricle and atrium points to the atrioventricular region, the wall between the atria is the interatrial septum, and the pericardium is the protective sac around the heart, not a septum.