Body Systems: Digestive System: Peristalsis

Although gravity aids in the swallowing of food, it doesn't work alone.  Our body actively pushes each food bolus through the digestive system, a process called peristalsis. 

Here's another hands-on model to help your students get a feel for peristalsis. 

The esophagus is made from a leg from a pair of tights or pantyhose.*

Cut the toe off in order to create a tube.

The food bolus is represented by a large plastic egg. 

Place the egg in one end of the tube.  Hold the 'esophagus' vertically so students can see that the food will not just fall through the esophagus - it's going to need a little help.. 

You can return the set-up to the table and have students determine the best way to move the food through the tube. 

They will quickly realize that the egg moves best when the tights/pantyhose above it are squeezed.

This is comparable to the muscles in the esophagus constricting and pushing the food throughout the digestive system.

Of course, we usually consume more than one bolus of food, so you can provide your students with a whole basket of eggs they need to get through the digestive system.  Create several set-ups and have teams of students race!


*Remember the plastic eggs that pantyhose used to come in, back in the day?  Those were the eggs I saw used in this activity originally.  I don't believe you can find those any more (at least without purging your grandmother's house), so I used a large-sized plastic Easter egg.  It works well, though its smaller than the original prop, and as such, you might want to use a child-sized pair of tights to make your esophagus. 

Body Systems: Digestive System: Digestion in a Bag

Students model both mechanical and chemical digestion with simple materials.

Each student needs a zip-top bag, one or two crackers (saltines work well) and a small amount of soda.

The crackers are placed in the bag. 

Students smash the crackers to represent mechanical digestion - breaking apart the food. 

A small amount of soda is added to the bag.  After observing for a  few moments, students and squish the contents of the bag.  The soda contains acid, like your stomach does, which helps break down the food even further.  Once the food has been turned into a slurry, it is ready to be passed on to the intestines.

Body Systems: Digestive System: Kinesthetic Model

 I love, love, love this activity from Bobbin Cave, part of the Access Excellence Fellows Collection.

Your students will actually act out the process of digestion - the props are so great and it's so much fun. 

First you'll need to make your food particle:

Place several M&Ms (or other brightly colored candy) in several small plastic bags (zip-top are preferable).

The bags of candy get placed in brown paper bags along with wadded up newspaper.

The paper bags, along with additional wadded up newspaper are placed in a large, thin plastic bag (you want something that rips open easily.

You'll need to gather some additional supplies:

--Large sponges

--Spray bottles filled with water - label half as "Saliva" and half as "Pancreatic Juices"

--Trash can

Use masking tape to make two parallel lines on the floor, 3 or 4 feet apart.

Have students line up, half on each line, facing each other. 

The path between them is the digestive tract.  They will all work together, using peristalsis, to push the food particle down the tract, as well as doing their individual jobs. 

Assign each student a job, based on his/her position along the tract. 

The first two students (the first student in each line) are molars.  Then saliva, pancreas, small intestine, blood, large intestine, and rectum. 

Double up on jobs as necessary to provide everyone with a role.  Explain what each student is responsible for doing in this activity:

• Molars: rip up food; the students will rip open the plastic bag when the get it
• Saliva: begins chemical digestion of food: the students will spray the bags and newspapers with their bottle
• Pancreas: continues chemical digestion of food; the students will spray the bags and newspapers with their bottles
• Small intestine: absorbs the nutrients and passes them to the blood; the students will search through the food particle to find the nutrients and hand the bags of nutrients to the blood
• Blood: distributes nutrients throughout the body; the students will pass out the nutrients to all the students (save this to do after all the digesting is complete)
• Large intestine: absorbs excess water; the students will use the sponges to soak up the water on the floor
• Rectum: removes waste: the students will place the remains of the food particle in the trash can

 I truly think this is a fantastic activity and is so useful in helping students learn the roles of the organs in the digestive system.  It takes a little bit of prep work (but not too bad) and if done properly, it cleans itself up! 

Body Systems: Digestive System: Digestive System Model

Use these props to help your students visualize the size of their digestive system.  This model is approximate for a 3rd grade student.

Esophagus: a straw

I was told that a straw is approximately the size of a 3rd grader's esophagus.  It seems like it might be a little narrow, but I can't find any exact figures to confirm or deny this.  My doctor brother-in-law says that the esophagus, when there's no food present, becomes pretty narrow, so this might be more accurate than I thought.

Stomach: small dish detergent bottle (sorry, the bottle accidentally got recycled... )

Here's a bonus to this prop: when it's empty and you squeeze it, it makes noise!  Just like your stomach!

Small Intestine: 24' of rope (about 1 cm diameter)

 Large Intestine: 6' of tubing (about 2 cm diameter)

Body Systems: Digestive System: Model Peristalsis

A 3rd grader's esophagus is about the size of a straw. 

Crumple up a small piece of paper and place it in one end of the straw (a clear straw is best for this).

Model peristalsis by squeezing the straw to push the paper all the way down the straw.