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When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.
Barbituric acid, the base material of barbiturates, was first synthesized in 1863 by Adolph von Bayer. His company later went on to synthesize aspirin for the first time, and Bayer aspirin is still a popular brand today.
When blood is deoxygenated and flowing back to the heart through the veins, it is dark reddish-blue in color. Blood in the arteries that is oxygenated and flowing out to the body is bright red. Whereas arterial blood comes out in spurts, venous blood flows.
Human kidneys will clean about 1 million gallons of blood in an average lifetime.