Since the heart is a muscle, it relies on the oxygen and nutrients contained in blood. This blood is supplied by arteries on the exterior of the heart -- when these arteries are blocked, a heart attack results. Take a look at our HowStuffWorks article to
Welcome to the daily audio workout for your head. Every day we have two games for you, each with three rounds which get progressively harder. To enjoy the full experience avoid distractions whilst you listen.
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