What are the major components of the cardiovascular system?

The cardiovascular system is primarily composed of the heart, arteries, veins, and capillaries. The heart serves as the central organ that pumps blood throughout the body, ensuring the delivery of oxygen and nutrients to tissues and the removal of waste products.

Arteries are blood vessels that carry oxygen-rich blood away from the heart to the various parts of the body, while veins transport deoxygenated blood back to the heart. Capillaries, the smallest blood vessels, play a critical role in the exchange of oxygen, carbon dioxide, nutrients, and waste products between blood and tissues at the cellular level.

The other options incorporate elements that are not primary components of the cardiovascular system. For instance, while the lungs are essential in the respiratory system for gas exchange, they are not classified as part of the cardiovascular system, which focuses on the blood and blood vessels. Similarly, the kidneys and spleen, while important organs within their respective systems (the renal system and the immune system), do not function as critical components of the cardiovascular system itself. Thus, the correct choice encompasses the fundamental elements involved in the circulation of blood, highlighting their interrelated functions.