According to the National Center for Biotechnology Information, the primary function of the circulatory system is to pass substances back and forth between blood and the body's tissues. The NCBL notes this system is also called the "cardiovascular system."
Clinton Community College identifies several exchanges between blood and tissue. For instance, blood carries oxygen from the lungs and delivers it all over the body. Blood also picks up waste, carbon dioxide, and brings it to the lungs for removal, states CCC. Blood also transports nutrients such as glucose, as well as hormones, according to the college. In addition, ammonia is picked up from tissues and taken to the liver for disposal. The CCC indicates that many animals maintain constant healthy body temperatures when heat is circulated through the cardiovascular system.