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How much blood do we have when the heart beats for the first time?

It should be between the third and fourth week of embryonic life.

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    $\begingroup$ Note: there is a heart "beat" but no pumping at 3-4 weeks. The blood vessels and chambers of the heart have not developed. The "beat" is just electrical activity in cells that will eventually become part of the heart. $\endgroup$ – Bryan Krause Feb 6 at 15:08
  • $\begingroup$ From your comment I guess we don't even have blood at 4 weeks $\endgroup$ – Zafalija Feb 6 at 16:43

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