Lungs and breathing

You can’t beat an easy lung dissection to get students interested and possibly a little nauseous! Hopefully at the time of writing there are still some actual butchers shops surviving out there and you have no problem getting your hands on some sheep or pigs lungs, especially if you have an obliging laboratory technician to help. Try to get some with oesophagus and trachea attached.
I usually set the lab up beforehand to look as much like an operating room as possible. A table at the centre covered in white sheets, stage lighting if available, and if you can get hold of some scrubs even better (although a lab coat and a stethoscope will do). Teaching is partly a theatrical performance after all! I normally have stools arranged around a central bench – “in the round” so to speak.
Start by bringing attention to the smooth surface of the lungs and discuss how this helps, along with the pleural fluid, 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 rib-cage – it’s much higher than most people imagine. Being a good physicist I will explain how the air is PUSHED into the lungs by the surrounding air pressure - “In Physics, there is no such thing as suck!”
Contrast the flexible cilia-lined trachea made of cartilage with the muscular lined oesophagus. You can remind them of peristalsis by squeezing a Smarty down the esophagus with your fingers (it’s 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 also to discuss the role of surface area in the functioning of the alveoli. Cut a piece of lung and put it on water to show how light it is compared with a piece of meat, which sinks. You can ask “What would happen if the sheep/lung had drowned?” I normally finish by cutting a cross-section across a whole lung horizontally to show the lung riddled with cartilage bronchioles, explaining that’s why we don’t normally eat lungs!
I will usually then get the students to do a “Draw the sentence” exercise (my favourite) where they convert 8 simple sentences about the action of the lungs into drawings.