Bell Jar Lung Demonstration Model (Jennifer Richard)

Author

Jennifer Richard, NBCT

Biology, Physiology, AP Biology, and AP Environmental Science Instructor

Chatsworth Charter High School

Principles

• Anatomy & Physiology

• Respiratory System

• Mechanisms of Breathing

Standards

9. As a result of the coordinated structures and functions of organ systems, the internal environment of the human body remains relatively stable (homeostatic) despite changes in the outside environment. As a basis for understanding this concept:

a.Students know how the complementary activity of major body systems provides cells with oxygen and nutrients and removes toxic waste products such as carbon dioxide.

Materials needed

• bell jar apparatus (jar, glass tubing)

• balloons

• rubber sheeting

Procedure

Have students study the model of the chest. The model is composed of the bell jar with a Y-tube to which balloons have been attached and a rubber sheeting seals the bottom.

Pull the rubber sheeting down to simulate the contraction of the diaphragm. Have students observe any changes.

Slowly allow the rubber sheeting to return to it's original position. Have students observe any changes any changes.

Explanation

The cavity inside the bell jar is airtight. As the diaphragm is pulled down, the volume of the cavity increases. This causes the pressure to decrease. Air rushes in to equalize the pressure, causing the balloons to inflate. As the diaphragm returns to it's original position, the volume of the cavity decreases. This causes an increase in pressure within the bell jar, the air rushes out of the balloons causing them to deflate.

This is an excellent model to use with classes studying animal respiration or health applications.

Questions

1. What does each part of the model represent?

   1. rubber sheeting = diaphragm

   2. balloons = lungs

   3. tube = glottis

   4. bell jar = chest cavity

2. Move the rubber sheeting down and describe what happens. Then, move the rubber sheeting back to it's original position and describe what happens.

   1. As the rubber sheeting is pulled down, the lungs inflate. As the rubber sheeting returns to its original position, the lungs deflate.

3. Repeat with the tube closed. Describe what happens.

   1. When the tube is closed, the lungs do not inflate as the rubber sheeting is moved down.

Everyday examples of the principles illustrated

Mechanisms of Breathing

Respiratory System

Photos

Movies

References

• Bell Jar Lung Model Wiki

• How Our Lungs Work

• Model of Lungs and Diaphragm

• Carolina Biological Supply Company