Transcript

CHERYL HAWKES

Today I’m going to show you how you can make your own lung in a bottle to better understand how changes in pressure drive air into and out of the lungs. For this activity, you will need a clear plastic bottle, about 500 millilitres, two balloons, some Blu-Tack with a hole in the middle, two small straws, or one large straw, and one pair of scissors. The first thing to do is to cut your bottle in half with the scissors, which can be a little bit fiddly, so I’ve made one already. And we’re going to use the top of it to make our model.

And next, take one of your balloons and cut the top of it off. I’m going to take this part of the balloon and wrap it around the base of the bottle. Next, we’re going to take the second balloon and insert it into the bottle.

And then wrap the lip of the balloon around the top of the bottle. Then, you take the two straws and cut them about a quarter of the way down. Next, we’ll insert the straws into the hole in the Blu-Tack, and put both of these into the mouth of the balloon. And then squeeze the Blu-Tack down over the straws and the lip of the bottle just to make sure that you seal off the bottle completely.

So here we have the model of the lung in the bottle where the straws represent the trachea, the balloon inside represents the lungs, the plastic represents the ribs and intercostal muscles, and the balloon at the bottom represents the diaphragm. Watch what happens when I pull up and down on the diaphragm-- you see that the balloon lung inside inflates as I pull down on the diaphragm. And that’s because when you do that the air pressure inside the lung is lower than the air pressure outside. And so the air flows down into the lungs.

When you press the diaphragm inwards, the balloon collapses, because the pressure inside the ribs is higher than the pressure outside. And this drives the air out of the lungs. So there you have it, your very own model of a lung in a bottle.