HSE INTERACTIVE MODULES

DEMONSTRATED BY DR. MICHAEL PARKER

Demo III: Change in Velocity - The Airways as Roads

Dr. Michael Parker chose this module to demonstrate how he sometimes draws on analogies when designing his animated diagrams. The physiological principle discussed here is the flow of gas molecules through the body's airways. When a person breathes out, air moves from the peripheral airways, which are the smallest air tubes at the outer edges of the lungs, to the central airways, the largest air tubes just before the mouth. Because a great many peripheral airways must "merge" into one central airway, the only way to maintain the flow of air is for the molecules to speed up as they enter the central airway. This knowledge is critical for patient care, as turbulence in the airways affects breathing and can have important ramifications for conditions such as asthma.

In order to illustrate this concept, Dr. Parker has created a module that compares the airways to roads and the air molecules to moving cars. In the diagram, single lane roads represent the lung's peripheral airways, and a two-lane highway represents one, large, central airway. At first, the animation can be configured so that two single-lane roads merge into the two-lane highway. In this scenario, cars moving from the smaller roads to the highway do not need to change their speed when they merge, since it's two lanes merging into two lanes. The flow continues unaffected. To make this scenario more realistic, students can click on the diagram and change the animation so that it has four single-lane roads merging onto the two-lane highway. In this case, in order to keep the flow of cars per minute constant, the cars must speed up when they reach the highway. This is analogous to the flow of air molecules in humans.

Key Lesson: A pitch-perfect analogy can help students visualize a difficult but important medical concept, in this case the flow of molecules through the body's various airways.