Blood is the medium in which dissolved nutrients, gases, hormones, and wastes are transported through the body. It has two major components: a fluid called plasma and specialized cells like red blood cells, white blood cells, and platelets that are suspended in the plasma. On the average, the cellular components of blood account for 40% to 45% of its volume, the other 55% to 60% are plasma. The average person has 5 to 6 liters of blood, constituting about 8% of his or her total body weight.