Which of the following is NOT a component of the cardiovascular system?

The cardiovascular system is primarily composed of the heart, blood vessels, and blood. Its main components include arteries, veins, capillaries, and the heart itself, all of which work together to circulate blood throughout the body.

Veins are responsible for returning deoxygenated blood back to the heart, while arteries carry oxygenated blood away from the heart. Capillaries serve as the site for gas exchange and nutrient delivery to tissues. Each of these components plays a critical role in maintaining effective circulation and ensuring that organs receive the necessary oxygen and nutrients.

Muscles, while crucial for overall bodily function, are not considered a direct component of the cardiovascular system. Instead, they rely on the cardiovascular system to supply oxygen-rich blood needed for energy production during physical activity. The muscles do play an indirect role in enhancing cardiovascular fitness by influencing heart rate and circulation during exercise, but they do not form a part of the cardiovascular system itself. Thus, identifying muscles as not being part of this system is accurate.