Classroom Digestion

Biology:	Digestive Tract
Grade Range:	Elementary School, Middle School
Format:	Hands-on, Stage

This is a good classroom demonstration which allows an entire class to participate. Be sure to ask about any allergies before performing this demonstration, and make sure you have enough candy for those who participate!

Materials

• Snack Size Candies
• Paper Lunch Bag
• Plastic Shopping Bag
• Paper Shopping Bag
• Two Small Spray Bottles

Safety Precautions

Please read the General Safety section of the Demonstration Safety page before performing this demonstration.

Before performing this demonstration, check with your event contact if there are any students with severe food allergies. Do not bring any candies that could trigger said allergies.

Demonstration

Preparation

• Put the candies into the paper lunch bag and seal it with tape. Put the paper lunch bag inside the plastic shopping bag and tape it shut. Put the plastic shopping bag inside the paper shopping bag and tape it shut. Fill the spray bottles with water.

Presentation (Stage and Hands-on)

Note: This demonstration does not work well for a science night or similar hands-on events, since it requires a large number of volunteers. Use this for hands-on events where you are working with small groups of students at a time.

1. Ask for volunteers from the audience. You will need 14 volunteers, so keep asking for volunteers until you have enough! Have the volunteers stand in two lines of seven, parallel to the audience, and give the two volunteers at the front of the lines the spray bottles.
   • If you are working with a class sized group (~30 or less), then you can have all the students participate. Have the extra students spread out between the 2nd, 3rd, 4th and 6th groups.
2. Explain to the volunteers that they will be acting like our digestive system, and will be "digesting" the food that you give them. Make sure they know that each volunteer will pair up with the one across from them.
   1. Give the paper bag to the 1^st volunteers. They will spray it down, then pass it to the next two.
   2. The 2^nd volunteers get to rip up the bag, but they do not rip it all the way open. After ripping a lot of holes in the paper bag, they pass it to the next two.
   3. The 3^rd volunteers rip the paper bag open, but they leave the plastic bag inside and pass it to the next two.
   4. The 4^th volunteers rip open the plastic bag, revealing the small paper bad inside. They leave the bags inside of each other, and pass it to the next two.
   5. The 5^th volunteers take out the small paper bag and open it, showing the candies inside. They give the candies to you, and then pass the three bags to the next two.
   6. The 6^th volunteers crumple the bags together into a small ball, and pass it to the next two.
   7. The 7^th volunteers take the crumpled up bags and throw them away.
3. Pass out the candies to the students who volunteered. Delicious science!

Why This Works

The Digestive Tract is the path through our bodies that our food takes when we eat. There are several steps to the digestion process, and this is a simplified way to look at that process. Below is a list of the steps and what part of the digestive tract they represent.

1. The first volunteers are the saliva in our mouths. Saliva helps to break down the outside of food, and provides lubrication so it slides more easily down our throat. Saliva is produced in a gland underneath the tongue, and is secreted from the cheeks and tongue.
2. The second volunteers are the chewing process. When we chew our food, we make it easier for the later processes to get to the nutrients inside the food. Our mouths have different kinds of teeth to help break down different kinds of food, and we have strong jaw muscles so we can thoroughly chew up and break down our food.
3. The third volunteers are the stomach. In our stomach the outer layers of the food are broken down further, exposing the inner layers where the nutrients are kept. The stomach produces hydrochloric acid, and the stomach lining is replaced every few weeks because our stomach acid is strong enough to break it down!
4. The fourth volunteers are the first step in our small intestines. Our small intestines break open the final layers of the food, revealing the nutrients that are inside. This happens because of various compounds that the body produces to help neutralize the acid from the stomach as well as the gut flora working to break the food down further.
5. The fifth volunteers are the second step in our small intestines. The small intestines extract the nutrients from food that our bodies can use and need, and works to extract as many nutrients as possible from it. Our gut flora also help with this, and some are able to produce vitamins for us while breaking the food down.
6. The sixth volunteers are the large intestine. The large intestine compresses the food waste (the bags) down, making it easier to remove it from our bodies. By this point, 60% of the waste is from old and dead bacteria cells from our small intestine, and the rest of it is food waste that our bodies cannot use.
7. The seventh volunteers are the rectum. The rectum expels the food waste from our bodies, which keeps out anything in the food that could be harmful if not removed. This also shows us an important fact about the digestive tract: the digestive tract is, essentially, a giant tube through the body! With the mouth as one opening and the rectum as the other, this tube allows us to take in food, extract the good parts, and remove the bad parts without the bad parts getting inside our cells or other organs!

Additional Information

• This demonstration can be paired with the Candy Conflagration to talk about how our bodies digest food and convert it into usable energy.
• Be sure to use candy that everyone can enjoy! Suggestions are snack size gummies and hard candies.