A model of the lungs

Activity 6.1 builds a model of how air moves in and out of the lungs.

Activity 6.1 — showing air movement

You will need: a small bell jar, a Y-tube, a stopper with a hole, two rubber balloons, a sheet of balloon rubber or polythene, some rubber bands

Set up the apparatus as shown. Pull the rubber sheet at the bottom downwards, then let it go, and watch the balloons.

Figure to be added

Figure 6.6 — the bell-jar model: a Y-tube through a stopper with a balloon on each branch, the bottom closed by a rubber sheet; (a) sheet pushed up, balloons small; (b) sheet pulled down, balloons inflated.

The observation

Pulling the sheet down increases the volume inside the jar, air rushes in and the balloons inflate. Letting it go reduces the volume, and air leaves the balloons.

In the model	In the body
Balloons	Lungs
Y-tube	Trachea and bronchi
Bell jar	Chest (thoracic cavity)
Rubber sheet	Diaphragm