Apologia General Science, Module 13, The Human Digestive System

►Videos and Resources for M13

First, a magic trick.
Watch this boiled purple cabbage water turn red the instant it hits the glass!

Wasn't that awesome!?!

Well... I didn't say the glass was empty.  =)
Actually, in the bottom of the glass was a teaspoon of the Works.  →
When I bought it, I made sure it had hydrochloric acid (also called hydrogen chloride), was non-clinging, and I thought it was colorless until it was poured.
It was clear-blue, but apparently it was light enough, because it worked perfectly.

So what does a 'magic trick' have to do with digestion???

Experiment 13.2 was about Stomach Acid and Antacids.
Stomach acid contains hydrochloric acid.
Purple cabbage juice can be used to measure pH, and indicate the presence of chemicals that are either an acid or a base.
The chemical in the cabbage juice that does this is called an indicator.
When the cabbage juice hit the hydrochloric acid in this toilet cleaner, it turned red!  I had hoped for at least pink, but this was great!  The white TUMS was to act as an antacid, but didn't dissolve readily.
So I did what my mom always did when we kids had to take medicine, but couldn't swallow pills yet.  I put a TUMS in a larger spoon, and crushed it with the back of another spoon.
Easy-peasy, powdered TUMS.
Dropping the powder into the red liquid gave us this instant, foamy result:

TUMS have an ingredient that helps to neutralize acid.  That ingredient is calcium carbonate.
Cabbage juice indicates the presence of a base by turning blue/purple.
I wish I had the whole thing on video from start to finish, but we had to figure out the crushed TUMS (In the video above, you can hear my pollen-induced laryngitis voice instructing them, lol).

Then we needed to find out what would happen if there was more hydrochloric acid than calcium carbonate.
So pretty...  =)



Before you even start eating, you smell food which triggers your salivary glands.  In saliva are enzymes that help you start digesting starches.
If you remember from the last module, starch is a polysaccharide (many sugars).  The enzymes in saliva break polysaccharides down into disaccharides.
So digestion starts in the mouth!

Just lovely.  bleh!

Experiment 13.1, Seeing a Part of the Digestive Process showed that saliva does indeed break down polysaccharides.
One of the boys chewed half a cracker, then spit it into a small dish and mixed it with a tablespoon of water.  The other half of the cracker was crunched it up in a baggie and also mixed it with a tablespoon of water.  A few drops into each dish, and you could see the difference.
Iodine is used as an indicator of starch.  When starch is mixed with iodine, the iodine turns the mixture a deep blue color, and this is what happened when the iodine hit the crunched up cracker mixture.
The iodine in the chewed cracker mixture turned kind of dark and brown.


(We had no results before when using clear iodine from my SIL on the potato in Experiment 9.2, Finding Food in Plants.  So I emailed Apologia about what kind to use, and they said either betadine or tincture of iodine work best.  So dh found this for me, and it worked.
It says 10% Providone-Iodine, and in the yellow circle it says Compare to Betadine® Solution Active Ingredient. 
I do not know what the bottle of clear iodine said on it.)


When your food gets to the stomach, it churns the food with gastric juice until it turns into a liquid mush called chyme (kime), then sends it to the small intestine.
The small intestine cannot work properly in the presence of acid.  So if your stomach contains acid, what happens to it?  The pyloric sphincter (a ring of muscles) allows small amounts chyme to pass in spurts into the top section of the small intestine, called the duodenum.  There, the pancreas produces a base called sodium bicarbonate that mixes with the chyme, neutralizing the stomach acid in the chyme.
God just thought of everything, didn't He?  =)


We skipped Experiment 13.3, because it seemed redundant to do it right after doing Exp. 13.2 (the Works and TUMS), and I just explained about the pancreas producing sodium bicarbonate that was a base just like the calcium carbonate in the TUMS.
Also we needed to play a game!  =)
The kids have learned to listen well, because they like chocolate!  =)
We went over the parts of the digestive system first, seeing what they knew and explaining all the parts of the diagram.

Yes, I know that the pink line indicating the digestive tract goes right through the trachea!
(choke, hack, suck air!)  The kids caught it and corrected me though. (yay!)

I had 6 kids and 18 labels (super-sticky notes, cut into thirds), so I divided the labels in to easy, medium, and hard.  One at a time, I gave each kid three labels, and they put them on the diagram.
If it was a small organ, they had to specify what they were labeling.  The other kids had to pay attention because we planned to do it a few times, and I would give them different organs each time.
After each turn, we went over the three labeled organs, and I gave points for correct answers.  After a couple of rounds, they were doing pretty good!

I got most of this diagram here (and tweaked the position of the pancreas to match our textbook), and added everything else from the neck up.

We learned about the role and composition of each of the organs of the digestive system, and that some organs were part of the digestive system, but not part of the digestive tract.
The salivary glands, liver, gall bladder, and pancreas contribute to digestion, but no food passes through them, so they are not part of the digestive tract.
Some of the organs on the diagram aren't part of the digestive system at all.  The larynx, trachea, and lungs are used for breathing.  We learned about them because of the need to differentiate between the larynx (top of the trachea) and pharynx (throat); the trachea (windpipe) and esophagus; and the soft palate (keeps food and liquid from going into the nose) and the epiglottis (keeps food and liquid from "going down the wrong way").

We also learned about the micronutrients, which are vitamins, and which were fat-soluble and which were water soluble, and a bit more about those.

I really liked this module, but some of the kids do not like talking about intestines and organs, LOL!
(I also watch documentaries about other body systems, or how the brain works, etc, and yes, my kids do think that's a bit strange, haha.)
I'm amazed at the complexity and know that only God could have created our bodies, that for the most part, work the same with each new baby born into the world.  =)


sMiLeS,