Some of the most important things your body does to keep you alive often go unnoticed. No longer. In this slideshow, we salute vital parts of your anatomy that only health professionals, science teachers, and biology majors often give thanks to.

It's Good to Have Soapy Lungs
The tiny air-sacs in your lungs known as alveoli are coated with a surfactant, a soap-like substance. It keeps the alveoli's delicate membranes--which measure less than half a millimeter thick--from sticking to each other when you exhale, emptying the oxygen from your body. You wouldn't want to use it to do laundry, but without it, you'd take exactly one breath--your last.