When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works. The circulatory system consists of three independent systems that work together: the heart ...

Take a deep breath — here's how the respiratory system works. When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works. The human respiratory system is a ...

The heart is a pump, and the blood goes round, and round, and round all the time. And why does it do that? Why can't it just have a rest? Well, the blood has to be kept moving around all the time ...

You remember how Dorothy, Toto, and the rest of the gang were trying to make their way to see the Wizard of Oz? That’s kind of how veins work in relation to your heart. Your heart is the wizard, and ...