When your heart was just a tube

I've been linking Double X Science a lot lately. That's because they're great. It's rare to get such smart, fascinating, science-centered discussion about female anatomy and reproductive issues that goes beyond the surface dressing we all already kind of know. Case in point: This piece by Emily Willingham about the development of the human heart in utero. You've probably heard at one point or another that a fetus' heart starts beating around 6 weeks (an age which is, by the way, calculated from the date of the mother's last period, NOT from the date of actual conception; so the fetus itself is really only about 4 weeks old at this point, and its mother only missed her period two weeks ago). But what's the heart actually like at that point? Turns out, absolutely nothing like what you imagine. Very cool stuff.