Investigation: How does Food Move in Your Esophagus?

Materials:   Timer, ruler, cups, stethoscope, aquarium tubing

Background information:   Food moves through the gastrointestinal tract by the peristalsis, where muscles constrict along the tube which pushes food from one area to the next.    Food first enters the GI tract when you swallow it and it goes into your esophagus.   In this investigation, you will determine if peristalsis occurs in your esophagus, or if fluid moves by gravity alone.

Procedure:

1.  Choose one person in your group to be the test subject.  Use a tape measure to determine the length of the esophagus.  Measure from the bottom of the chin to the bottom of the sternum in centimeters.

Length of Subject’s Esophagus: ___________  (cm)

2.  Have the subject get a cup of water.

3.  Place the stethoscope near the sternum and slightly to the left, which is the approximate location of the cardiac sphincter valve.  This valve opens to allow food into the stomach.   You can hear the sound of the opening and closing with the stethoscope.

4.  As the subject swallows the water, listen to the stethoscope, you will hear the opening of the valve as a kind of gurgle.  This may take some practice.

5.  Once you have practiced the procedure, you will time how long it takes for food to move through the esophagus.     Have the subject stand up and take a drink of water without swallowing; then swallow the water when you say “go” and start the timer.  

How long does it take for the valve to open? _____________ (sec)

Calculate the speed of water:   Speed =  Distance /  Time          __________    cm/s

6.  Repeat step #5, but have the subject lay across the lab table (or floor).  

How long does it take for the valve to open when lying down? _____________ (sec)

Calculate the speed of water:   Speed =  Distance /  Time          __________    cm/s

7.  Compare the speed of water movement in the esophagus to the movement by gravity alone.  Use an aquarium tube and water to determine how fast water will move by gravity alone.  ( Your instructor may demonstrate this for the class.)

            What is the length of the tube? ___________        Time it takes for water to leave the tube:   _____

            Calculate the speed of water in aquarium tube:  Speed =  Distance /  Time              __________    cm/s

Analysis:

1.  CLAIM: Does food move through your esophagus by gravity or by peristalsis?

2. EVIDENCE:  Use your data from the investigation to support your claim.   (Explain how you know this.)

3.  How reliable is your data?  What could you do to make the data more reliable?

4.   Could a person stand on their hands and still swallow fluid?      Explain your answer.

5.  Propose a way to determine how quickly food will move through the small and large intestine.  For example, how could you find out how long it took you to completely digest a hamburger?