The cardiovascular system is composed of the heart and the network of arteries, veins, and capillaries that transport blood throughout the body. The average adult male has between 5 to 6 liters of blood or blood volume, while the average adult female has between 4 to 5 liters. The blood carries oxygen and essential nutrients to all of the living cells in the body, and also carries waste products from the tissues to the systems of the body through which they are eliminated.
Most of the blood is made up of a watery, protein-laden fluid called plasma. A little less than half of this blood volume is composed of red and white blood cells, and other solid elements called platelets.
Linda J. Vorvick, MD, Medical Director and Director of Didactic Curriculum, MEDEX Northwest Division of Physician Assistant Studies, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, David R. Eltz, Stephanie Slon, and Nissi Wang.