We just learned about how the blood flows through the ventricles, atriums, veins and arteries.
In between each of these areas is something called a valve which opens and closes to let the blood out or keep it in.
![heart valve](https://upload.wikimedia.org/wikipedia/commons/thumb/3/35/Blausen_0459_Heart_VentriclesContract.png/576px-Blausen_0459_Heart_VentriclesContract.png)
(from: wikipedia - heart valve)
Kid Facts - Blast from the past: Common Carotid Artery