Well, I asked him to teach me what he knows:
First your food goes in the mouth and you crunch it up small enough to swallow. Then, you get it down into the esophagus. It's something you push, push, push, push down into the stomach. The stomach can drift down into the small intestine. Now the small intestine is a river that flows to the large intestine. The large intestine is so stinky! Because there's POOP inside! Back to the stomach. We'll teach you that the stomach can let everything down to the liquid part of feel. In the small intestine, the food will be soaked up into villi. It gets delivered to all parts of the body in veins and with arteries. What gets sucked out in the large intestine is water. The extra water goes into the tube, gets through the kidneys, and then it goes into the bladder. When that happens, you start to tinkle. Even the food in the large intestine can get pushed out of your body too. But when that happens, that is not tinkle. It's... POOP!
Here in the breathing, your air goes down the trachea, which is not like the esophagus, as the esophagus pushes it down, and the trachea doesn't push the air down. You breathe, and the trachea blows it down like the three little pigs. Like the wolf blows down their houses. Like it does to the trachea, as it blows the air down into the body. And the part in the body that it goes into is the lungs. And there's another part of the body that's air. It's red and it's liquid. When you get a cut, you'll see it bleeding sometimes and you'll see some scrapes sometimes. And you can not see it when you don't have any cuts. It's about the good blood and the bad blood. And there's the heart. First, the bad blood goes into the heart, and then it goes into good blood. What helps it is the lungs. And then it comes out of the heart, and then it comes into the body!
And there's something else about the digestive system. Girls have three holes, and the boys have two holes. Both the boys' holes are to the digestive system. And the girls don't have all their holes to the digestive system. They just have one hole to the reproductive system. The reproductive is where the baby comes out. You'll see it so tiny, the size of a baby dolly. And they have just two holes to the digestive system.