509. A joke about heart sounds

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There are two heart sounds heard when listening to a healthy human heart:

S1, which comes from your mitral and tricuspid valves closing, stopping blood from back-flowing from your ventricles to your atria, and…

S2, which comes from your aortic and pulmonic valves closing, stopping blood from back-flowing from your pulmonary artery and aorta into your ventricles.

Normally, the aortic and pulmonic valves close at about the same time, and you just hear one sound, S2.  But sometimes, they close at different enough times that they sound separate.  This is a splitting of S2!

There are a lot of reasons why this could happen.  You could have a hole in your heart between your two atria or between your two ventricles.  This would send more blood to the right side of your heart, and your pulmonic valve would stay open longer to get it all out.  If you have this, it is called a fixed splitting of S2, and it is a pretty bad thing to have!

But another way you can get more blood to the right side of your heart is just by breathing in.  This sucks blood into your lungs from your abdomen, and the blood goes through your right heart on the way to the lungs.  This would cause the pulmonic valve to stay open longer, too.  If you have this, it is called a physiologic splitting of S2, and it doesn’t have to be such a big deal.

But if you knew that all already, maybe you would have liked this pun on the word “inspiring”!  I have a test on all this tomorrow and I hope it goes well.

In other news… Cowbirds in Love now has a store.