You'll need:
~10" foam pipe insulation
~10" 1 1/2" PVC pipe
Model Magic clay
red yarn
fabric pieces
Begin with the length of foam pipe insulation to use as the spongy bone. Split the insulation open to reveal the hollow tube in the center, perfect for holding the bone marrow.
Roll the clay into a snake that fits the center of the pipe insulation. While you're rolling the clay, embed a length of red yarn in the clay to represent a blood vessel traveling through the marrow.
Slide the completed spongy bone and marrow into the length of PVC pipe. This is the compact bone.
Use the fabric to create a tube into which the PVC pipe can slide. This is the membrane covering the bone.
I added a few pieces of Velcro, to attach the blood vessels.
I'm really quite pleased with my model. It can be taken apart and put back together again and again and I think it will be quite useful in the classroom.
Because you usually have to buy 10' lengths of PVC that you have to cut yourself, some of you might be turned off by this project. I've got extra materials from making my own, as well as easy access to additional supplies, and a willingness to make up some additional models. If you're interested in purchasing a pre-made model (or several), send me an email and we can discuss the details.