Circulatory System
The Circulatory System is an organ system that distributes blood and other nutrients like oxygen and acids to other organs. In the Circulatory System, humans and other vertebrates have a closed circulatory system, the blood never leaves the veins and arteries. Invertebrates have a open circulatory system, blood flows to every part of the body. Adults have 5 liters of blood making up 7% of their body weight. Our kidneys use up 20% of our blood flow ( cardiac output).