What Happens When You Eat?

Kelly Ludwig                   Lincoln-Way High School
                               1801 East Lincoln Highway
                               New Lenox IL 60451
                               (815) 485-7655

Objectives:

     These activities will show students what organs aid in digestion and how 
digestion occurs in the human body.  This lesson maybe appropriate for middle 
grades, but is designed for the upper grade curricula.

Materials Needed:

Activity #1:  How Long is the Digestive System?
     - yarn (at least 4 different colors)

Activity #2:  Digestion
     - sugar cubes
     - granulated sugar
     - 2 clear cups filled with water

Activity #3:  Carbohydrate Digestion
     - unsalted soda crackers (2 per student)

Activity #4:  Hands on Digestion
     - a small lump of hamburger (meatball size)
     - one plastic baggie
     - 1M HCl 
     - Digestive Juice A (pepsin, trypsin and water)
     - Digestive Juice B (bile salts, pancreatin enzyme and water)
     
Activity #5:  How do Villi aid the Small Intestine in Absorption?
     - paper towels (10 per group)
     - 4 cups of an equal amount of water
     - graduated cylinder

Activity #6:  A Digestive System Simulation
     - large thin plastic bag            - newspaper
     - paper sacks (2 sizes)             - Zip-lock bags
     - M&M's candy                       - masking tape
     - markers & paper                   - sponges
     - trash can                         - labeled spray bottles of water

Strategy:

Activity #1:  How Long is the Digestive System
     Have students cut a piece of yarn according to the following measurements.  
Allow students to use different color yarn to represent different organs.  After 
the yarn has been cut tie the pieces together.

                 Esophagus               25 cm
                 Stomach                 20 cm
                 Small Intestine        700 cm
                 Large Intestine        150 cm
              
                 TOTAL                  895 cm

Activity #2:  Digestion
     Place a sugar cube in a cup of water.  Place about a spoonful of granulated 
sugar in the other cup of water.  Observe what happens.

Activity #3:  Carbohydrate Digestion
     Have the students chew two unsalted soda crackers for two minutes without 
swallowing.

Activity #4:  Hands on Digestion
     Place the hamburger, 3 eyedroppers full of 1M HCl, one tablespoon of 
Digestive Juice A and two tablespoons of Digestive Juice B into a plastic bag.  
Knead the bad with your hands (simulates the stomach) for about 10-15 minutes, 
it will have been reduced to mainly liquid and have a definite odor.

Activity #5:  How do Villi aid the Small Intestine in Absorption?
     Compare how 1, 2, 3, and 4 folded paper towels absorb.  Dip each paper 
towel into a cup of water (use the same amount of water in each cup).  Record 
the volume of water left in the cup (using a graduated cylinder).

Activity #6:  A Digestive System Simulation
Procedure:
Things to make ahead of time:
  1.  FOOD TUBE:      Lay out two parallel lines of tape on the floor, 3'      
                      apart and long enough for half the class to stand 
                      shoulder to shoulder on one side of the parallel 
                      lines.
  2.  FOOD PARTICLE:  The food particle consists of M&M's placed in 
                      small zip-lock bags.  These are placed in wadded
                      newspapers in small paper sacks.  Place the small
                      sacks in larger sacks with added newspaper.  Place
                      all sacks and add newspaper until the large 
                      plastic bag is full.  This bag is then taped or 
                      tied closed to complete the food particle.
Action:
  1.  Peristaltic Movement:  Put the food particle to be eaten at one end of the 
      food tube and a large trash can at the other.  Have students line up on 
      both sides, facing each other, squeeze the food particle the length of the 
      food tube. 

  2.  Digestion:  Label and/or instruct the players.  As the food comes to a 
                  student they should narrate what they are doing and why.

           Teeth - tear food apart (break plastic bag)
           Saliva - use spray bottles to moisten food particle
           Stomach - tear small bags apart
           Pancreatic juices - spray food
           Small Intestine - absorbs food, find bags of candy and pass to blood 
                             (the teacher can play the role of the blood)
           Large Intestine  -  reabsorbs water, sponge up water on the floor
           Rectum/Anus - puts the waste papers in the trash can

Performance Assessment:

     At the completion of this lesson students should be able to answer the 
following questions:

     1.  What system in your body is the same length as the completed piece of 
         yarn?  What is it's length (in centimeters, in feet)?
     2.  From your observations in Activity #2, what can you conclude must be 
         done to food before digestion begins?
     3.  What physical and chemical changes occurred to the soda cracker?
     4.  What caused the physical and chemical changes to the soda cracker?
     5.  Did you notice a taste change in the soda cracker?
     6.  How was mechanical digestion simulated in Activity #4.
     7.  What evidence was their that chemical digestion occurred in the 
         hamburger?
     8.  Which paper towel had the largest surface area?
     9.  Which cup had the highest volume of water left?
    10.  How do the villi (of the small intestine) aid in absorption?
    11.  Follow the path of a food particle through the digestive system;
         include the organs and their functions.

Conclusion:

     These six activities will enhance the student's knowledge of what organs 
aid in digestion and how digestion occurs in the human body.  Students will have 
a more comprehensive understanding of what happens in their bodies when they 
eat.