Which of the following refers to one of the two lower chambers of the heart?

The term that refers to one of the two lower chambers of the heart is "ventricle." The heart consists of four chambers: two upper chambers known as atria and two lower chambers called ventricles. Each ventricle has specific functions; the right ventricle pumps deoxygenated blood to the lungs, while the left ventricle pumps oxygenated blood to the rest of the body.

To provide clarity on the other terms: atria are the upper chambers responsible for receiving blood; the aorta is the large artery that carries oxygenated blood from the left ventricle to the body; and the septum is the thick wall that divides the left and right sides of the heart, preventing the mixing of oxygenated and deoxygenated blood. Understanding the structure of the heart and the roles of its components is essential in emergency medical treatment, as it aids in diagnosing and managing various cardiac conditions.