First Line of Defense
Chapter 32: Immune System

As you may recall, the job of the body's first line of defense is to keep pathogens out. This role is carried out by the skin, mucus, tears, and sweat. Mucus coats the openings of some parts of the body, such as your nose and mouth, to prevent pathogens from gaining entry. You can model the function of mucus if you…

Try This

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1. Copy the data table shown onto a separate sheet of paper.

   Condition	Time to inflate balloon (in min.)	Time to deflate balloon (in min.)
   Empty straw
   Honey in straw

   
   
2. Using scissors and a metric ruler, cut strips of construction paper to make a ring 2.5 cm wide and 25 cm in diameter. Tape the strips together to form the ring.
3. Modify two balloons by inserting a straw 2.5 cm into the opening of each balloon. Secure each straw with a rubber band. Be careful not to crimp the straw.
4. Hold the paper ring directly in front of you. While a second person times you with a watch with a second hand, inflate one of the balloons until it just fills the ring. Pinch the balloon shut. Record the time it took you to inflate the balloon in the data table.
5. While measuring the time, release your hold on the balloon and allow it to deflate. Record the time it took for the balloon to deflate in the data table.
6. Squirt honey into the straw in the other balloon until the straw is entirely filled. Repeat steps 4 and 5.

Analyze Your Results

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1. What did the honey represent?
2. Which balloon took the most time to inflate and deflate? Which one took the least time?
3. How does this activity model the role of mucus in the immune system?

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