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
What does each part of the model represent?
rubber sheeting = diaphragm
balloons = lungs
tube = glottis
bell jar = chest cavity
Move the rubber sheeting down and describe what happens. Then, move the rubber sheeting back to it's original position and describe what happens.
As the rubber sheeting is pulled down, the lungs inflate. As the rubber sheeting returns to its original position, the lungs deflate.
Repeat with the tube closed. Describe what happens.
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