What components make up the circulatory system?

The circulatory system is composed of three main components: the heart, blood vessels, and blood. The heart functions as the pump that propels blood throughout the body. Blood serves as the transport medium that carries oxygen, nutrients, hormones, and waste products to and from cells. Blood vessels, which include arteries, veins, and capillaries, form a complex network that facilitates the flow of blood, allowing it to reach all parts of the body.

This selection emphasizes the integral role each component plays in maintaining the circulatory process. The heart pumps the blood, which travels through the vessels, ensuring that every tissue receives the necessary substances for proper function while also removing waste. Other options reference structures related to the circulatory system but do not encompass its entire framework. For instance, including lungs pertains more to the respiratory system, and mentioning brain or tissues relates to their functions rather than the components making up the circulatory system itself.