What does the circulatory system consist of?

The circulatory system consists of the heart and blood vessels, which are crucial components for transporting blood throughout the body. The heart acts as a pump that circulates blood, delivering oxygen and nutrients to tissues while removing carbon dioxide and waste products. Blood vessels, including arteries, veins, and capillaries, form a network that facilitates this circulation. This system is essential for maintaining homeostasis, providing a means for the distribution of hormones, and playing a key role in immune function.

In contrast, the other options listed do not contribute to the circulatory system's primary function. The lungs and airways are part of the respiratory system, which focuses on gas exchange. The brain and nerves make up the nervous system, responsible for transmitting signals throughout the body, while the skin and muscles belong to the integumentary and muscular systems, respectively, which play roles in protection, movement, and regulation. Each system has distinct functions that contribute to overall body health, but it is specifically the heart and blood vessels that define the circulatory system.