What is the main function of the circulatory system?

The main function of the circulatory system is to transport blood, nutrients, and oxygen throughout the body. This system plays a crucial role in maintaining homeostasis and ensuring that all cells receive the necessary substances to function properly. Blood is the primary transport medium, carrying oxygen from the lungs to the tissues and removing carbon dioxide produced by cellular metabolism. Additionally, the circulatory system is responsible for distributing nutrients absorbed from the digestive tract to various cells and tissues, as well as transporting hormones and waste products.

While other options mention important functions within the body, they are not the primary role of the circulatory system. Digestion and respiratory functions primarily involve other systems, such as the digestive and respiratory systems, respectively. Regulation of body temperature, although it involves circulation (e.g., blood flow adjustments), is a secondary function among many integrated processes managed primarily by the skin and hypothalamus. Thus, the primary focus of the circulatory system is indeed on transportation and distribution within the body.