Digestion starts in the mouth. I asked the girls to break up a few Graham Crackers into bite sized pieces into a bowl. This was our "mouth". Next, we added water for saliva and used a pastry blender for teeth.
I didn't have an esophagus for this demonstration, so we just talked about the food going down the esophagus to the stomach.
Our "stomach" was a zip lock bag. The stomach digests food by 1)gastric juices (I just squirted some lemon juice for the gastric juices) and 2) by the muscles churning the food for several hours. We took turns churning the food with our hands acting as the stomach muscles.
Here, I took the opportunity to talk about involuntary muscles vs. voluntary muscles.
Next, I poured the churned food mixed with saliva and gastric juices into a spice ball made of mesh wire to demonstrate how the intestines absorb nutrients and water.
Your intestines are 22 feet long!
Everything in the bowl stays in the body, but that which is not absorbed is poop.
I asked them if they wanted to hold the poop and they were soooooo grossed out, until I said, "This is only pretend poop. Smell it." It smelled like cinnamon Graham crackers. They all wanted to hold the poop then. (giggles)