Modeling the Lung

Subject Area	Biology - Physiology
Age or Grade	Introductory Biology – Grades 9 +
Estimated Length	1 hour
Prerequisite knowledge/skills	Students should be familiar with basic respiratory anatomy: lungs, trachea, bronchi, diaphragm
Description of New Content	This hands-on activity demonstrates the basic anatomy and function of the lungs. Students will gain a concrete understanding of how muscular expansion and contraction of the chest cavity allows the lungs to inhale and exhale air.
Goals	To demonstrate the process of inhalation, exhalation.
Materials Needed	Per group of students (3-4 people per group) 1) 2 plastic straws (no bendable joints) 2) 2 small balloons 3) 1 large balloon 4) Rubber cement 5) 2 small rubber bands 6) 1 large rubber band 7) Empty 2 liter plastic bottle 8) Scissors 9) Modeling clay
Procedure	To create the lungs: 1. Take a piece of straw about 2 inches in length and cut a small triangle in the center, but don't go through to the opposite side. Fit one small balloon over each end of the straw and secure it with a small rubber band. (Make sure that air will go into each balloon when blown from the top.) 2. Bend the straw in the middle of the hole. 3. Take a second piece of straw and cut a V-shape on the end. Fit the slanted points of the straw into each semi-circle of the hole of the bent straw. 4. Cement the two pieces of the straw together. Allow to dry or use tape to hold until dry. To create the chest cavity 5. Cut off the bottom of the plastic bottle 6. Insert the lungs into the bottle, allowing the top straw to stick out of the mouth of the bottle by at least 1 inch. 7. Use modeling clay to seal the mouth of the bottle with the straw in the center. Make sure that there is an air-tight seal, so that air can only get into the bottle through the straw. 8. Cut the top off of the large balloon, and stretch it over the bottom of the plastic bottle. Secure the balloon with the large rubber band. 9. Push on the rubber at the bottom of the bottle. What happens? Is this like breathing in or out? Pull the rubber down. Which way would you be breathing now?
Evaluation	Students will answer these post-lab questions 1) What muscle the big balloon represent? What is the role of this muscle in breathing? 2) When the diaphragm is extended, do the lungs fill up with air or expel air? Why (hint: think vacuum cleaner)? 3) What body part(s) do the straws represent? 4) In the lung model that you built, why is it important to create a seal over the neck of the plastic bottle? What would happen during “breathing” if there was a leak? 5) What if one of the lung balloons became punctured? Would it still change volume in response to the movement of the diaphragm? 6) What does the plastic bottle represent in this model? (hint: it protects the balloon lungs, and controls how far they expand)
Extensions
References	“Modern Biology” Textbook, Wikipedia