Circulate this news: the heart is a pump containing one-way valves! Following the previous activity on the external structure of the heart, learners now take a look at the inside. They use a three-color diagram to label a black-and-white photograph of a human heart cross section. If working through the entire unit, they also take time to add to their concept maps. When you want to get deep into the heart with your middle schoolers, this activity will take you there!