What's the difference between an artery and a vein?

 An artery carries blood away from the heart; a vein carries blood to the heart.

Explanation: Veins carry blood towards the heart. This blood has given most of its oxygen to the body, so it is low on oxygen and high in carbon dioxide. It enters the right side of the heart and travels to the lungs. There, the lungs eliminate carbon dioxide and exchange it for more oxygen. The oxygen-rich blood enters the left side of the heart. Then, arteries carry blood away from the heart. Pulmonary circulation brings blood from the heart to the lungs and back. Systemic circulation brings blood from the heart to the rest of the body and back.

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lunar landing mission. apollo 11 was the first manned mission to land on the moon. the first steps by humans on another planetary body were taken by neil armstrong and buzz aldrin on july 20, 1969. the astronauts also returned to earth the first samples from another planetary body.

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