Which body system is primarily responsible for transporting oxygen and nutrients to cells throughout the body?

The circulatory (cardiovascular) system — the heart, blood, and blood vessels — transports oxygen, nutrients, hormones, and waste products throughout the body. The respiratory system (lungs) brings oxygen into the blood and removes carbon dioxide, but the circulatory system does the actual delivery to cells. The digestive system breaks down food into nutrients, and the nervous system handles signaling. These systems work together, but transport of oxygen and nutrients to cells is the circulatory system's main job, carried by the blood the heart pumps.