Tiffany did a unit in science about the digestive system. It was fun. She and Katie took some crackers, a banana, and a little water and mashed them inside a plastic baggie to simulate the stomach grinding up food. It totally looked like vomit when they were done.
Part of the unit said to make a model of the digestive system by connecting panty hose to a balloon, to something else, etc. It was really a lot of work that I'd have to do for this model, and I didn't see a huge payoff for it. Instead, I turned to youtube. I found a perfect video with a catchy tune. Needless to say, the kids loved it! They asked me to play it over and over. They asked for it again days later. I finally had to bookmark it, so I didn't have to search for it anymore. Tiffany has now memorized most of it.
Here's the video. Beware, it can be addictive for small children.