Esophagus: a straw
I was told that a straw is approximately the size of a 3rd grader's esophagus. It seems like it might be a little narrow, but I can't find any exact figures to confirm or deny this. My doctor brother-in-law says that the esophagus, when there's no food present, becomes pretty narrow, so this might be more accurate than I thought.
Stomach: small dish detergent bottle (sorry, the bottle accidentally got recycled... )
Here's a bonus to this prop: when it's empty and you squeeze it, it makes noise! Just like your stomach!
Small Intestine: 24' of rope (about 1 cm diameter)
Large Intestine: 6' of tubing (about 2 cm diameter)
