Which component is NOT part of the circulatory system?

The lungs are not considered a part of the circulatory system; instead, they are an integral component of the respiratory system. The primary role of the lungs is to facilitate gas exchange, allowing oxygen to enter the bloodstream and carbon dioxide to be expelled.

In contrast, the heart, blood vessels, and blood all play crucial roles within the circulatory system. The heart acts as the central pump that drives blood throughout the body, while blood vessels, including arteries, veins, and capillaries, form the network through which blood circulates. Blood itself serves as the medium for transporting oxygen, nutrients, hormones, and waste products throughout the body.

Understanding the distinct functions of these systems is key to grasping the overall workings of human physiology.