Deep breath, kids, and take a butcher's at this

You can't beat an easy lung dissection to get your students interested - and possibly a little nauseous. But you have to do it well. Here's how my lesson works.

First, visit a local butcher's shop (hopefully there is still one near you) to get your hands on some sheep or pig lungs. Try to get those with an oesophagus and trachea attached.

Before the lesson, set up the lab to look as much like an operating room as possible. Place a table at the centre, cover it with white sheets and illuminate it with stage lighting. If you can get hold of some scrubs, even better - although a lab coat and a stethoscope will do. Arrange stools around the central table.

Start the lesson by bringing pupils' attention to the smooth surface of the lungs. Discuss how this, along with the pleural fluid, helps the lungs to move in relation to the rib cage. Remind the class of the role of the diaphragm contracting beneath the lungs and the intercostal muscles expanding the rib cage. Show where approximately the diaphragm is in relation to your own rib cage - it's much higher than most people imagine. Explain how the air is pushed into the lungs by the surrounding air pressure.

Next, contrast the flexible cilia-lined trachea made of cartilage with the muscle-lined oesophagus. You can remind students of peristalsis by squeezing a Smartie down the oesophagus with your fingers; when it appears at the other end, you might see a few green faces. Discuss the role of cilia in keeping dirt particles out of the lungs - and how smoking can affect their action.

Before cutting the lung itself, inflate it using a blower; cue a couple more green faces. Then cut down the trachea with scissors, branching off into the bronchi, remembering to discuss the role of surface area in the functioning of the alveoli. To show how light the lung is, cut off a piece and float it on some water. Draw a comparison with a piece of meat, which would have sunk.

Finally, cut a cross-section across a whole lung horizontally, showing pupils how it is riddled with cartilage bronchioles. Explain that this is why we don't usually eat lungs.

As a plenary, get students to take part in a "draw the sentence" exercise. They must convert eight simple sentences about the action of the lungs into drawings.

Simon Porter works for international schools group Nord Anglia Education

To download the plan for this lesson, visit www.tesconnect.comMyBestLesson

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