Teeth and dental health - Use models of tooth anatomy and lower molar. Talk about dental health - brushing, flossing, fluoride rinse. Let bone in soda or a variety of liquids for days or week and see what effect it has. See what happens to the unprotected part of the egg. Egg shells also contain calcium.
Valves keep blood going right way.
Make models from The Body Book or sketch illustration. With no instruments students can find pulse and count before and after walking or running, noting increase. You could make bar graphs, comparing these or other things, or line plots of all the data. Use Stethoscopes to listen to heartbeat and use sphygmomanometers to measure blood pressure. Try to get school nurse or other medical person to help and who could better discuss what blood pressure means.