Wow! Muscles in my stomach?

Zach and I read 'The Magic School Bus: Inside the Human Body.' We had a great time on our field trip with the Friz. I love reading to Zachary. Not only is he a sponge but his questions are so much fun! I told him that he has muscles all over his body. He looked at me in amazement. He started looking all over himself and asked if he has muscles in his stomach, his leg, his mouth? Yes, you do! Oh, he was shocked, lol. Five is such a fun age. I often wonder if he just humors me. He's seen this book on DVD and we've talked about it before but he still seemed shocked to hear all this information he's heard many times before.