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Цусны эргэлтийн тогтолцоо, гүнзгийрүүлсэн хичээл

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Your heart sits in the middle of your chest and pumps blood from about 4 weeks after conception until the day that you die. This little pump is the size of your clenched fist and it never stops. Watch these videos to learn more about how the heart works, blood flow in arteries and veins, blood pressure, and lymphatics.