The circulatory system (also known as the cardiovascular system) is one of the organ systems of the body, the primary function of which is to transport blood and nutrients around the body. It is comprised of the heart, blood vessels and blood.
Humans (along with the majority of mammals) possess a double circulatory system. The pulmonary circuit transports deoxygenated blood to the lungs so oxygen can move into the blood and carbon dioxide can be removed, before the oxygenated blood is transported back to the heart where it can be moved around the body via the systemic circuit.
The cardiovascular system is also involved in the transport of nutrients, hormones, waste products, and white blood cells throughout the body, to assist with its normal and healthy functioning.