Between the two lower chambers sits the

Between the two lower chambers sits the

• A. interventricular septum
• B. interatrial septum
• C. atrioventricular valve
• D. Chordae tendineae

Answer: (A)

Between the two lower chambers sits the interventricular septum, the thick muscular wall that separates the right ventricle from the left ventricle. This divider keeps blood on the right side from mixing with blood on the left, which is essential for proper pulmonary versus systemic circulation. The interatrial septum sits between the atria, not the ventricles. The atrioventricular valves (the mitral and tricuspid valves) lie at the junction between each atrium and ventricle, not between the ventricles themselves. The chordae tendineae are the tendinous cords that anchor valve leaflets inside the ventricles. So the structure between the two lower chambers is the interventricular septum.