In biology, a vein is a blood vessel which carries blood toward the heart.
Veins form part of the circulatory system.
The vessels that carry blood away from the heart are known as arteries.
Veins have one-way valves to prevent backflow caused by gravity.
For more information about the topic Vein, read the full article at Wikipedia.org, or see the following related articles:
Editor's Note: This article is not intended to provide medical advice, diagnosis or treatment.
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