Photo by Annie Spratt
BLOOD
The old saying is true – blood is 6 times thicker than water.
Everybody produces more than 1,000 pounds of red blood cells in a lifetime. These cells live for four months on average; travelling between the lungs and other tissues 75,000 times. Then they return to the bone marrow to die.
Karl Landsteiner discovered the different blood types in 1900.
One heartbeat pumps about five tablespoons of blood, and this amounts to 2,000 gallons of blood each day. You receive a complete new bloodstream every three months, and the amount of blood within your body, about 7% of your body weight, is essentially constant.
In terms of chemical composition, human blood most closely resembles seawater.
Since the different blood types were discovered, Type A-H, the rarest type, has been found in less than a dozen people. Type O is the most common blood type.
Every square inch of human skin consists of an astonishing twenty feet of blood vessels.
Having picked up carbon dioxide and other wastes from the body’s cells as it circulates, blood is a purplish, blue colour in the veins as it returns to the heart. It is red only in the arteries when it is full of oxygen when leaving the heart. This means that blood is red in only half your body, but wherever cut yourself you will bleed red because the blood is instantly exposed to oxygen.
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