#9 The Digestive System

Review
We began by reviewing the body systems from The Human Body Part I, completed earlier in the school year.

The Great River

The Circulatory System

The Nervous System

The Eye

The Vestibular System

The Ear

The Endocrine System

Photosynthesis and The Respiratory System

Day One Story & Exploration
I took my story for The Digestive System from Linda Allison's book, Blood and Guts: A Working Guide to Your Own Insides.

The chapter is called "Digestion: Down the Food Tube." I required that the older students take notes during the lesson.

I started by asking the students to brainstorm what parts they thought were in the digestive system. Their answers were liver, bowels, stomach, throat, belly button, tongue and chest. One student volunteered that she thought there were two tubes in the throat, one for food and one for water.

We read page 75 (Which Bunch Are You For Lunch?) and then did the Keeping Track activity on page 77. I gave them the stethoscope and let them each listen to their bodies digesting their lunch. (I recommend doing this after lunch; I chose 1 pm). Then I read page 76 (Breakdown) and showed them the diagram on page 77 (Charting the Food Tube). I wrote all of the parts in our food's path on the board.

Mouth
(mechanical breakdown with teeth and tongue,
chemical breakdown with saliva)

Esophagus

Stomach

Small Intestine
(food is actually absorbed into the body here)

Large Intestine
(extra water is absorbed here)

Rectum

Anus

We answered all kinds of practical questions. If you ignore your defecation reflex and let your food sit in your large intestine, more and more water will continue to be absorbed and it will get harder and harder. Thus, constipation.

I pointed out to my students that they already know a lot about their digestive system just from being alive. You know from throwing up, for example, that your food gets more "liquidy" from being in the stomach.

We also talked about how pregnant women can't possibly have babies growing in their stomachs, because stomachs are full of acid!!!! So, obviously, this happens in another part of the body. They were very interested in the idea of the umbilical cord carrying oxygen and nutrition to the developing baby and carrying waste away, so we spent some time on this. I also explained that the growing baby takes up a lot of room so pregnant women have a lot of heartburn. One student had already brought up how heartburn is caused by overeating and having too much food in your stomach. It's also caused by the crowding of the baby!

We also talked about the mucus lining which protects the stomach, and how an ulcer is when the stomach acid does eat a hole in the stomach wall.

Two students then demonstrated the power of peristalsis with the activity 4.1 from Easy Genius Science Projects with the Human Body: Great Experiments and Ideas. Yes, you can swallow even when you are standing on your head! This demonstration is a lot of fun.

We moved on to page 78 (Amazing Enzyme) and page 79 (Chemical Lunch). I wrote on the board

Carbohydrates - fuel

Protein - building blocks for growth

Fats - energy production

Then we did the Test for Fat from the Kitchen Chemistry activity on page 79. This is so easy and only requires a brown paper bag. I cut a large piece from one side of the bag and laid a variety of foods on it, labeling each location with a pencil. We did a piece of cooked venison, butter, cold cereal, some shredded lettuce, and sour cream. After the students saw that there was a ton of fat in butter and sour cream, I asked them if they knew how butter was made. No one did. So we made butter. This takes only some whipping cream, a large jar (I used a half gallon jar so the cream would fill with plenty of air), and some patience. The kids were SO EXCITED when it worked! We all had bread with fresh butter to celebrate.

While the group was passing around the jar and shaking it vigorously, I read them the remainder of the chapter. This was pages 80 (Riddle of the Sphincter, Solid Waste), 81 (Bacteria for Life, Natural Gas, Cooking with Gas: A Natural Fact), and 82 (Special Events, Amazing Facts).

I ended the day by having the students work together to paint the beans needed for the "Make Your Own Nutrition Balance" activity from The Human Body: 25 Fantastic Projects Illuminate How the Body Works. I recommend five green beans, seven yellow beans, three blue beans, and six red beans.

Day Two Review & Exploration
First thing in the morning we talked about the Food Guide Pyramid and I drew it on the board. Then I showed my students how the beans we painted yesterday were going to help me see if I had a balanced diet that day. We talked about how your diet needs to be balanced in more than one way. You need to have ENOUGH food, NOT TOO MUCH food, and a VARIETY of food. Throughout the day I put the appropriate colored beans in the pan balance as I ate. Having the 21 unpainted beans weighing down one side of the scale at the beginning was really helpful. It reminds you that you really do need to eat -- no matter how busy we get as adults -- because your body needs a certain amount of energy to function. You have to put those calories in there.

In the late morning we came back to the topic of The Digestive System. Before my students went off to write their rough drafts and begin their illustrations for the main lesson books, I wanted to do one more demonstration. This is on pages 78 and 79 of Blood and Guts. I have several suggestions if you're doing this with a class. It is totally worth doing but...

First, it helps to make up the cornstarch/boiling water concoction in advance. It needs time to cool.

Second, make sure you do not have decolorized iodine. It will not work. (I got my true-blue iodine at Walgreens.)

Third, demonstrate the iodine test for starch (page 79) with more than one food. I used a regular baked potato and a sweet potato at first, until I realized that my kids probably think that iodine always turns black on any food. So then I put a drop into some yogurt and they saw that it is usually a caramel color.

Fourth, it take a LONG time to get a tablespoon of saliva. So either start early in the day, if you're only collecting from yourself, or be prepared to pass the tablespoon around the class and let everyone spit into it. Gross.

So, we did the Enzyme Action activity on page 78 and it was totally AMAZING. Seriously. This is a MUST-DO! I had already cut the side of a bunch of Styrofoam cups up for the upcoming Teeth activity later in the day, so I used the bottoms of the cups for the Enzyme Action test and they worked like a charm. Everyone could see the colorful results against the white of the cup, and they're easy to number and keep organized.

While the saliva was doing its job, we reviewed the parts and function of the digestive system by looking at the nomenclature three-part cards from ETC Montessori. I laid out and matched the pictures and definitions, and passed out the vocabulary cards to the group. As I showed each picture and read each definition, the child who had that vocabulary term came forward.

We also looked at The Digestive System page in our atlas of the human body, the Wall Chart of Human Anatomy.

Main Lesson Book
Students began to draft their summaries and illustrations for The Digestive System.

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