Using inquiry and a little bit of mystery the students learned about how the circulatory system worked.  The students were given a colour on their hand which told them where they needed to stand and the job they needed to do.  The students completed one round before they figured out that they were acting as the circulatory system and pumping blood around the body.  They understood the connection between the heart and the lungs and how they transferred oxygen and removed carbon dioxide.  Each body part had to work very hard and, hopefully, we gained a little admiration for all the work our body does for us to function.