A Trip Through the Digestive System (Apologia A & P)

It was my turn to organize the project/lab for our co-op of Apologia’s Human Anatomy and Physiology.  We just finished Chapter 4 on the digestive system where the suggested project was to make a digestive themed amusement park.   That seemed a little more “arts & crafts” than science to me  so I went in search of something better—AND FOUND IT!   I found my inspiration from two websites: O2 learn has a great video of the process, but no materials list (you’ll want to watch it for her great British accent anyway);  Squidoo has a similar lab (with a materials list), but it leaves out some steps and relies on a blender-- which we don’t have in our bodies.   So this is my mish-mash of the two.  WARNING: You may not want to read this post soon after eating, there are pictures of the process. 
Andrew Pudewa of IEW once said that a great way to engage kids who’d rather build forts all day was to make sure the subject was either funny, dangerous or gross.  This activity falls into the last category…it was so engaging that my Schnickelfritz forgot to start taking pictures until half way through.  Just what I want as a teacher, but bad for blogging so I recreated some of the first steps for this post. 
This is a fairly inexpensive project since you’ll probably find most of what you need in your house already.  The foil pans you’ll see below came from a catered dinner – I just picked out the pans in the best shape and washed them up.  I’ve used them for several years of science co-op.  They’re big enough for two kids to work at each and allow me to work with liquids away from the sink.  The person transferring the mixes from stage to stage may want a pair of gloves – rubber gloves for dish washing or plastic gloves from a hair dye kit.  My husband the Toolman had just had surgery and the nurse let me have a few pairs from their supply drawer.

THE MOUTH

Supplies	Equipment
soft foods	A bowl or tray
drink	kitchen shears
water mixed w/ laundry detergent	potato masher

 
We begin with our lunch—a PB&J sandwich (great way to use up the heels which no one our house likes), a banana, and some grape-aid.   Use whatever you have handy but try to keep it soft – it needs to be smashable so no carrots. You could probably add tortilla or potato chips which would dissolve with liquid. My inspiration sites used a can of spaghetti and oatmeal.   I did go buy the drink packet, but didn’t waste any sugar since no one would actually be consuming it.

The kitchen shears represent the incisors – cutting the food into bites.  Pour some of the beverage in as well.  This is still too big to swallow so we’ll begin to smash everything with the potato masher, playing the role of the molars.   The water/detergent mixture represents saliva so pour some of that in now.  Our detergent happens to be clear but if yours is colored don’t worry – we’re hoping to achieve a brown outcome so the more colors the merrier.  Just remember all the liquid you add now will need to be removed in the small & large intestines so don’t add too much (we still have more to add later).  Everything is now poured into a Ziploc bag.

THE STOMACH

Supplies	Equipment
Acidic liquid	1 Gal. Ziploc bag
green food coloring

 

 

When you close the Ziploc bag, make sure to remove most of the air.  Otherwise when you start kneading the bag it may pop and we don’t need any reverse peristalsis here.  We’ll also be adding something to represent stomach acid.  One site used apple cider vinegar, but we happened to have just polished off a jar of dill pickles so I used that juice instead.  Given a little time and an enthusiastic lab assistant you can create a fairly smooth chyme.  I also added green food coloring to represent bile.  This doesn’t happen in the stomach (and I explained that to the kids)  but it is easier to mix the color in at this stage.

 

THE SMALL INTESTINE

 

 

Supplies	Equipment
no new supplies	leg from pantyhose
	a deep tray to catch liquid
	rubber or surgical gloves
	canning funnel

Next time you get a run in your hose you might want to save it to stand in for the small intestine.  I didn’t have one so we used an old knee-high stocking.   The funnel is really there for ease of transfer but you could mention it is playing the role of the sphincter, although it isn’t able to open and close like a real one could.

Pour the chyme into the stocking over a tray because the liquid will start coming out immediately.  Poor Mr. B in the photo above  was thoroughly grossed out at this point, but he couldn’t resist watching his younger brother squeeze the mix through the intestine (he even managed to smile).

The more liquid you manage to get out at this point, the less you’ll have to deal with in the next stage so you might want to expound on the process at this point and let the mix drain.  You can either cut a hole the the toe of the stocking and push the mix through (more accurate), or roll the stocking up like you were going to put it on and then invert the mix out at the top.

THE LARGE INTESTINE

Supplies	Equipment
no added supplies	a plush towel
	a deep tray to catch liquid

 

 

Empty the contents of the stocking onto a folded towel.  We’re going to wring the towel to remove more of the liquid just like what occurs in the large intestine.  I used a very old towel for this part but after the lab it came out of the laundry perfectly clean.  As long as you haven’t gone overboard with the food coloring and Kool-aid you should be fine.  Open the towel and put the contents into a plastic bag for the final stage.

The Rectum

Supplies	Equipment
no added supplies	a plastic  bag
	a  tray or plate

 What started out as lunch looks essentially done at this point and you could stop, but I used a gray shopping bag to represent the rectum.  In hindsight that wasn’t the best choice as the bag just stretched and the mix came out in the same lumps we had from the large intestine.  Perhaps we’d squeezed out too much water or perhaps we needed  less flexible material.  We could have used a cloth pastry bag –there weren’t any toxic materials used.
In the end, nobody was too grossed out – in fact some of the boys are holding the end results in the photo and Schnickelfritz is just hamming it up for the camera.  It will be some time before they forget our trip through the digestive system.

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