Blood is the fluid in the body that is used to transport oxygen, nutrients, and waste products between tissues and organs. It’s also a vital part of the body’s immune system.
By volume, blood is 55% plasma, 45% erythrocytes (red blood cells), and less than 1% leukocytes (white blood cells) and platelets. Healthy adult human males have between five and six liters of blood, while healthy adult females have a little less, between four and five liters.
- ↑ Human Anatomy and Physiology, by Elaine N. Marieb, RN, PhD, Benjamin/Cummings Publishing Company, 1995