eis 29: the digestive system
Activity 1: Food to Poop
Thorough digestion is absolutely essential to good absorption of nutrients: after all, you can’t just fit a whole piece of broccoli or a chunk of steak through your cell membranes! So, before food gets to the all-important absorption phase in the later part of the small intestine, it has to be broken down first in the mouth (mechanical digestion and chemical digestion of carbs), then again in the stomach (mechanical digestion and chemical digestion of proteins), and finally in the first part of the small intestine (this is where most digestion happens!).
This activity will give you the chance to model these steps in your own hands. Hope you like a little mess!
This activity will give you the chance to model these steps in your own hands. Hope you like a little mess!
materials
- 3 small mixing bowls and a plastic baggie (or a frosting bag). If you prefer to keep your hands clean, you can use 3 plastic baggies in place of the mixing bowls (for a total of 4). Quart-size works best.
- Crunchy, carby food. Chips, crackers, and cereal all work nicely. About a cup is great.
- Water. About a cup should work well.
- Lemon juice or vinegar.
- Liquid soap. You only need a drop or two.
- A cheesecloth or a fine mesh sieve.
- A piece of fabric or paper towels,
- A spoon may be helpful but not absolutely mandatory.
procedure
1. Place the food inside the first mixing bowl or quart-sized plastic bag ("mouth") and begin to crush it. Occasionally add water (“saliva”), up to a few tablespoons, to the mix as you continue mushing. This will simulate the processes of mechanical and chemical digestion. This mush is called a “bolus”.
2. Transfer the bolus to a new mixing bowl or quart-sized bag ("stomach").
3. Add a small amount of lemon juice (acid), up to a few tablespoons, and water (“trypsin”—an enzyme used to break up protein), up to about a half cup, into the mix, and squish it until the food has a liquid-like texture. This mush is called “chyme”.
4. Carefully transfer your chyme into the third mixing bowl or quart-sized bag (“small intestine”).
5. Add more water (“ digestive enzymes”), up to about a half cup, and soap (“bile”), up to a few drops. We use soap because it works in a very similar way as bile. This mush is still called chyme.
6. Filter your mush loosely through a fine-mesh sieve or cheesecloth. This models the process of absorption. The liquid is the “absorbed nutrients” in your food.
7. Filter the remaining mush through a paper towel or piece of fabric. Squeeze out as much liquid as you can. This models the process of water reabsorption.
8. Place the solid into the last clean plastic bag or frosting bag (the "rectum").
9. Cut a hole at the end of the plastic baggy (if you’re not using a frosting bag, which should already have a hole).
10. Squeeze the solid out of the bag. This models the process of defecation (pooping). Is your “poop” liquidy or solid?
If you’re having fun, we want to see it! If you have an Instagram and the permission of your relevant responsible adult, share with us @eons_learning, #FoodToPoopEons.
2. Transfer the bolus to a new mixing bowl or quart-sized bag ("stomach").
3. Add a small amount of lemon juice (acid), up to a few tablespoons, and water (“trypsin”—an enzyme used to break up protein), up to about a half cup, into the mix, and squish it until the food has a liquid-like texture. This mush is called “chyme”.
4. Carefully transfer your chyme into the third mixing bowl or quart-sized bag (“small intestine”).
5. Add more water (“ digestive enzymes”), up to about a half cup, and soap (“bile”), up to a few drops. We use soap because it works in a very similar way as bile. This mush is still called chyme.
6. Filter your mush loosely through a fine-mesh sieve or cheesecloth. This models the process of absorption. The liquid is the “absorbed nutrients” in your food.
7. Filter the remaining mush through a paper towel or piece of fabric. Squeeze out as much liquid as you can. This models the process of water reabsorption.
8. Place the solid into the last clean plastic bag or frosting bag (the "rectum").
9. Cut a hole at the end of the plastic baggy (if you’re not using a frosting bag, which should already have a hole).
10. Squeeze the solid out of the bag. This models the process of defecation (pooping). Is your “poop” liquidy or solid?
If you’re having fun, we want to see it! If you have an Instagram and the permission of your relevant responsible adult, share with us @eons_learning, #FoodToPoopEons.
Activity 2: Guts and Bolts
We’ve seen a lot of processes that happen in the human body. Negative pressure breathing, heart beating, capillary transport, signalling in the brain, and now digestion. Sometimes it’s important to take a step back from the details and remember the big picture of how all these processes fit together: Your brain provides the signalling that your body needs to function and adapt to a changing environment; your body can then pump blood to the lungs, where it picks up oxygen and drops off carbon dioxide, to the small intestine, where it picks up nutrients, and to the liver and kidneys, where wastes are detoxified and excreted; meanwhile, blood gets pumped all over the body, dropping off these nutrients and oxygen and picking up wastes and carbon dioxide from every last tissue that needs it—including your brain, completing the cycle and allowing it to do a lot more complicated things, too.
All in all, you’re a bit like a very complicated machine. This activity is a fun online game that will help you to see how all of your “guts and bolts” come together to form you. It starts off simple to give you the idea of how the game works, and then adds extra layers until you’re including many of your different body systems. This game will require an understanding of how blood flows and what the function of each major of each major organ is.
All in all, you’re a bit like a very complicated machine. This activity is a fun online game that will help you to see how all of your “guts and bolts” come together to form you. It starts off simple to give you the idea of how the game works, and then adds extra layers until you’re including many of your different body systems. This game will require an understanding of how blood flows and what the function of each major of each major organ is.
Longitudinal Activity: Making a Model of the Human Body
Add the following structures to your model of the human body:
- Mouth
- Salivary glands
- Esophagus
- Stomach
- Small intestine
- Pancreas
- Liver
- Gallbladder
- Large Intestine
- Rectum