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How many litres of blood does the adult human body contains ?

In humans, blood is the fluid that transports nutrients and oxygen to every cell in the body. It also transports wastes away from cells. Blood keeps our body temperature steady by carrying excess heat from regions of the body to the skin where it can be dissipated. It also fights infection and carries chemicals that regulate many body functions.

Blood is composed of a yellowish fluid, called plasma, in which are suspended the millions of cells that constitute 45% by volume of whole blood. A cubic millimeter of human blood contains about 5 million red blood cells, or erythrocytes; 5,000 to 10,000 white blood cells or leukocytes; and 200,000 to 300,000 platelets or thrombocytes. The blood also carries many salts and organic substances in solution in the blood plasma.

In an average healthy adult, the volume of blood is about one-eleventh of the body weight. Most sources state the volume of blood in an average human adult, who is between 150 to 160 pounds, as between 4.7 and 5 liters, although the more recent sources state the volume of blood in an average adult as 4.7 liters. Sources state that an 80-pound child had about half that amount, and an 8-pound infant has about 8.5 ounces. People who live at high altitudes, where the air contains less oxygen, may have up to 1.9 liters more blood than people who live in low altitude regions. The extra blood delivers additional oxygen to body cells. The heart pumps all the blood in the body each minute when the body is at rest.


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