The average person has about five liters of blood constantly being pumped through the arteries and vessels to every organ and cell in the body. And blood travels fast. It takes only about a minute for a drop of blood to whip around the body.
Blood supplies the body with oxygen, food and other nutrients and takes away waste products.
These functions are performed by the red blood cells. White blood cells, with their capacity to mount a concerted attack against literally thousands of invading organisms, play an important defensive role. Rather than being an inert liquid, blood is a living entity, teeming with specialized cells. Blood can be separated into about three liters of plasma and two liters of cells. The plasma is liquid derived from the intestines and organs of the body.