The Digestive System

So last week we were studying the Circulatory and Respiratory systems.  This week, we have moved on to the Digestive system.  (again, thank all that is good we are in life science...I am rockin' out the instruction here ;)  ) Though there is nothing revolutionary to report, these are all simple things that you can do in your own class during your unit.

We started with my favorite.....BrainPOP.  The video on the Digestive System has just enough information to give the kids a basic understanding of how it all works.  While they were watching, I had them labeling a little picture of the system in their science journals.

During science lab, we modeled the process of digestion.  To do this model, you will need for each student/group of students:

2 baggies
cracker
tablespoon of water
shot glass size of orange juice


First, the students placed the cracker into the baggie and started to mash it up with their fingers.  This was the "mouth" part of digestion.  Then, adding water, we showed how the saliva makes the cracker mushy enough for the tongue to push it back into the esophagus. 

Once it enters the stomach, acid interacts with the mush.  The kids then added the OJ.  The muscle action of the stomach is then shown by the kids "kneeding" the baggie.  For some of my kids, their bag began to leak..probably due to the previous grinding and the added acid.  We discussed how the stomach would do that too were it not for the special mucus.  To simulate the mucus, we just placed the baggie and all of its contents inside of a second baggie.  Leaking problem solved and the kids learned a bit about the power of the acid!


Next, we talked about how that all entered the small intestine and the nutrients were absorbed.  To demonstrate *why* the small intestine is all smushed up, I took a long piece of construction paper.  I told them to imagine it was the small intestine.  We thought back to math and our discussions on surface area.  It made sense to the kids that since the nutrients were passing over the small intestine, it would want the most surface area possible to grab the important food for the cells.  I then accordion folded the construction paper to show how much smaller it would become by being folded altogether.  In order to take up the same length as the orginal piece, I would need to use 3 more accordion folded strips.  That is 3 times the surface area to pick up nutrients.  The kids had this lightbulb moment right then and there!

Finally, the food moves into the large intestine.  I will warn you, this part was messy, gooey, and a bit gross....but the kids LOVED LOVED LOVED it.

I explained that once all the nutrients were sucked out of the chyme (the name of the stuff in the small intestine) all that was left was a watery mass of waste.  Well, we know from previous studies that our body is 70% water.  If we just got rid of all that water, we would be dehydrated in no time.  So the large intestine's job is to suck all that water back into the body.  I took some oatmeal that I had previously made to simulate the waste/water combination.  Then, I poured it into a pantyhose.  Using my own two hands, I squeezed out as much of the water as possible.  Here was the end product.

I told you, it came out looking gross...but the kids got the point.  The understood the main purpose of the large intestine, and we even were left with some waste to "eliminate" through the rectum.  And no, I did NOT demonstrate that ;)

Next, the students broke out their Human Body Systems slide project that they have been working on already and began the Digestive and Excretory systems slides. (they started with circulation and respiration)  The kids were VERY into these two slides.  I mean, they do have some poop talk involved in both of them....so naturally these slides caused a lot of giggles and fun ;)

I then had the students create their own digestive tract using a their own picture!  The kids LOVED this one, as they love anything that involves themselves ;)  The kids wrote all of their knowledge about the various parts of the digestive system and glued it all together as if they were the body model.

The final piece was to write a narrative story as if they were a piece of food going through the digestive system.  The kids got super creative with this and, using the organizer I created, were very well organized with their stories!

So there you have it.  Some simple, yet effective ways to teach the digestive system.  Would you like the EXACT lessons that I used?  I have compiled them all here, including all of my graphic organizers, a close reading passage, anchor chart samples, and more here for you.