What term refers to the entire system through which blood circulates in the body?

The term that refers to the entire system through which blood circulates in the body is the circulatory system. This system is responsible for transporting blood, nutrients, oxygen, carbon dioxide, and hormones to and from cells throughout the body. It includes the heart, blood vessels (arteries, veins, and capillaries), and blood itself, working together to maintain homeostasis and support bodily functions.

While the cardiovascular system, which specifically focuses on the heart and blood vessels, is often used interchangeably with the term "circulatory system," the latter is broader and encompasses the complete network of blood circulation. The other options, such as the respiratory system and nervous system, serve different functions—breathing and gas exchange, and communication and coordination within the body, respectively—and are not focused on blood circulation.