We had a rather disgusting afternoon on Monday, making our own digestive systems. The children were given some crackers (food), water (saliva) and orange juice (stomach acid) to mix together in a plastic bag (the stomach). This caused problems for some groups, as over-enthusiastic mixing caused the bags to break!
After squashing the mixture down, we transferred it into the leg of a pair of tights (intestines) and squeezed out all of the liquid. When it reached the end, we cut a hole and, yes you guessed it, out it plopped! Ew!