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Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
If all the neurons in the human body were lined up, they would stretch more than 600 miles.
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.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
Illness; diuretics; laxative abuse; hot weather; exercise; sweating; caffeine; alcoholic beverages; starvation diets; inadequate carbohydrate consumption; and diets high in protein, salt, or fiber can cause people to become dehydrated.