What is the key function of the circulatory system?

The key function of the circulatory system is to transport oxygen, nutrients, and waste products throughout the body. This system, comprising the heart, blood vessels, and blood, plays a vital role in maintaining homeostasis by delivering essential substances to cells and removing metabolic waste. Oxygenated blood from the lungs is transported to cells to support metabolism, while deoxygenated blood carries carbon dioxide and other waste products back to the lungs and excretory organs for removal.

While respiratory gas exchange is important, it primarily involves the lungs rather than the circulatory system directly. The circulatory system does assist in this process by transporting oxygen-rich blood from the lungs to cells and returning carbon dioxide back to the lungs but doesn't facilitate gas exchange itself.

Regulating body temperature and producing hormones are also functions related to the circulatory system, but they are not its primary role. Body temperature regulation can occur through the circulation of blood and the distribution of heat, while hormones are transported via the circulatory system but are produced by endocrine glands. These functions are secondary to the overall purpose of transporting essential materials throughout the body.