Artificial Lung - (Brent Shano)
Author
Brent Shano, Medical Magnet Science Teacher, Van Nuys High School
Principles
Pressure Differentials
Inhaling / Exhaling
Muscle Contractions
Standards
Investigation & Experimentation:
1. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other four strands, students should develop their own questions and perform investigations. Students will:
d) Formulate explanations by using logic and evidence.
g) Recognize the usefulness and limitations of models and theories as scientific representations of reality.
Materials needed
Plastic cup
Two balloons
One straw
Tape (any type should be sufficient)
Scissors
Glue / some sort of silly-putty / play-dough for stopping air flow in gaps between straw and cup
Procedure
The quick instructions on how to build the model of the lung can be found in the "movies" section below.
To demonstrate inhaling: pull down on the "diaphragm" the balloon piece at the bottom of the cup.
To demonstrate exhaling: let go or release the "diaphragm"
Continue in as many steps as needed.
Be sure not to pull to hard on the diaphragm so as to break the model.
Side Note: The "Lung", the balloon on the inside of the cup, will not stay full of air even when the diaphragm is contracted aka pulled down. Be ready to explain why.
Explanation
A lot of students think that when we drink out of a straw that we are "sucking" the fluid into our body. This is a misconception. Actually we are creating a pressure differential (one area has a greater or higher pressure than another selected area.) In fact the fluid in our drink is actually being "pushed" into our mouths by atmospheric pressure.
How does this relate to our study here? Just ask a kid how they breathe and try not to laugh at their response. Some students might even infer that our shoulders have something to do with it. When my shoulders go up the air goes in, and when they go down the air goes out. This just simply is not the case. We breathe very similarly to the way we drink out of a straw.
When the diaphragm below our lungs contracts (it lowers) is creates a lower pressure in our lungs and air from the outside of our bodies comes in to fill that void. Remember from Biology: that things tend to go from areas of high concentration to low concentration naturally. The processes that take place in the lungs are a story for another time, but once that diaphragm is done contracting, it relaxes. Upon relaxing it goes up and the air in the lungs is exhaled, once again due to a pressure differential. This process continues for your whole life and is automatic. It's controlled by your nervous system and is one less thing you have to consciously think about.
Questions
Q: What is the muscle underneath the lungs that is responsible for us breathing?
A: Diaphragm
Q: Why do the lungs expand?
A: The air from the outside comes rushing in and since air occupies space the lungs are forced to expand.
Q: Why is it a good thing that our rib cage is not just made of bone?
A: Bone is hard in nature and not very flexible. The cartilage near the sternum area allows for some flexing and bending which in turn compensates as we inhale and exhale.
Q: When the diaphragm is relaxed (up position)... Where is there greater pressure, on the inside or the outside?
A: Inside (that's why air doesn't come in. Not until the diaphragm contracts does air come into the lungs again from outside the body)
Everyday examples of the principles illustrated
Animals breathing
Drinking out of a straw.
Scuba Diving
Being an Astronaut in Space
Photos
