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Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
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.
Not getting enough sleep can greatly weaken the immune system. Lack of sleep makes you more likely to catch a cold, or more difficult to fight off an infection.
Never take aspirin without food because it is likely to irritate your stomach. Never give aspirin to children under age 12. Overdoses of aspirin have the potential to cause deafness.
The first successful kidney transplant was performed in 1954 and occurred in Boston. A kidney from an identical twin was transplanted into his dying brother's body and was not rejected because it did not appear foreign to his body.