The heart is the body's hardest-working muscle. Whether you're awake or asleep, or exercising or resting, your heart is always at work. It pumps blood through arteries to deliver oxygen to organs and ...
Laid end to end, an adult's blood vessels could circle Earth's equator four times, with scientists estimating anywhere between 60,000-100,000 miles of blood vessels in the human body. Your heart ...
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