We did a one day unit study of some of the basics, and although he knew about most of them already from reading or absorbing everyday knowledge, it was a nice project to give him a visual and give a little introduction of the underrated organs that he didn't know too much about (such as the gallbladder).
We used the science workbook My Body, which had copies of each organ and a detailed description of the functions. We made copies so he could color them in and then we could still read the book afterwards for review.
We taped it up on the wall for a couple of days (supposedly safely away from puppies, although Lucy finally ripped a corner so it is down now). The organs were taped so you could lift them up and view the others underneath.
whole body view
He was glad to get this finished, and we will be reviewing the different systems of the body in the Giant Science book. W already read about the Skeletal system, and with Halloween on its way watching our annual favorite The Skeleton Dance was an inspiring and silly way to bring it up.