Teacher Monica Chrambach talks about the limitations of the model she uses to help teach her seventh-grade students about the digestive system in this video segment from Teaching Middle School Life Science. She details some of the limitations and the ways in which it can be misleading, and she demonstrates how she uses class discussion to review the deficiencies. She also explains that models like this one cannot always be complete because the students have yet to learn about certain related aspects, such as some of the more advanced chemistry involved.