[Originally posted 8/5/2007]
This is part of the medical ethics thread but I had to put it in the "awesome creation" title. I wanted to digress just slightly to marvel at the awesome body God has created. Having a PFO made me realize some more details of our incredible body.
I'm no physiologist so many of you may correct me. But here's what I've been able to figure out.
When our heart develops in the fetus, there is a passageway in the septum between the right and left atria. This allows blood in the fetus that returns to the heart through the veins to pass through the passageway and be pumped directly to the brain and the rest of the body. The lungs of the fetus are not in operation, being sequestered in the womb. Hence, the blood cannot/should not/needs not pass through the lung for reoxygenation. The mother performs that function (I haven't figured that one out yet!) somehow.
Upon birth, the lungs begin to operate and the mother's helpful action is no longer available. At that point, the blood needs to circulate through the lungs. The heart then sends the blood to the lungs and gets it back before shipping to off to do its work in the body. The passageway, known technically as the foramen ovale, is no longer needed and it closes. In several months, this opening is usually sealed.
However, in what is estimated to be 25-30% of the population, the opening does not close completely. The seal leaks and blood can pass from the right to left atria, bypassing the cleansing action of the lung. Typically, this is not a very significant amount and no problems occur. But statistically, there is a higher risk of "paradoxical emboli", or stroke of unknown origin.
What amazes me is how the entire process works. What an incredible way God has made us! To think that a valve is open just when it is needed to provide a crucial shunt and then it closes to provide an important seal is absolutely amazing. Any engineering project with such a goal would need some pretty fancy controls to ensure that this happens appropriately.
We continue to learn amazing things about our body. What reaction can we have but to worship our God who has made us in such a wondrous way.