I took some science classes bac in 2008/09. One of the exams papers was make a 3D biology model.
I chose to knit the digestive system. I am quit prod of it as it is a full scale model. This means that you can lay it in on an small adult or a child and see that it fits. You can feed it with ceramics beans. Just put it in the mouth and it will pass trough the digestion system and come out looking as feces in the end. The whole model is knitted in wool and cotton.

The model is fixed to a plate of polystyrene with needles. This way I can unhook it and use it in the classroom.

First I knitted a long tube with only 4 stitches. This was later rolled up and sewn. Doing it this way to get the flexibility of the intestine that can be stretched both longitudinally and in across, to simulate the peristale movement (bowel movement). Oral cavity, throat, stomach and duodenum was knitted with straight stitches(3mm) because the bowel movement is not important in this part of the digestive system.

The plate of polystyrene is intended for storage. The model is taken down when it is used and hung up when lessons/play is finished. The model works both when it is on the plat and when it is taken down. As a display you can add names to and as a tactile model to see and feel how the digestive system work.

Creating this model did take much time. It is not difficult but enormously time-consuming. Should I have knitted a new digestive system, I would have chosen a thinner yarn and I would have made more stitches. The movement of intestinal section would have been much better. I would also have chosen to separate the different parts with different colour so that they would be easier to identify. Maybe this type of project is something you can do together with friends or collage.