What are the major components of the circulatory system?

The major components of the circulatory system are the heart, blood, and blood vessels. The heart serves as the central pump that circulates blood throughout the body, ensuring that oxygen and nutrients are delivered to cells while carbon dioxide and waste products are removed. Blood is the fluid that carries oxygen, nutrients, hormones, and immune cells, and it plays a crucial role in maintaining homeostasis. Blood vessels, which include arteries, veins, and capillaries, form the network through which blood flows, connecting the heart to various tissues and organs.

In contrast, while the lungs are vital for gas exchange, they are part of the respiratory system, not the circulatory system. Additionally, the spleen is an organ involved in immune function and blood filtration but is not a primary component of the circulatory system itself; instead, it functions alongside it. Therefore, the combination of heart, blood, and blood vessels accurately captures the essential elements necessary for circulation within the body.