Lesson overview

In this lesson students will explore the respiratory system and learn how gaseous exchange occurs in the alveoli. They will then examine and label a practical diagram and describe adaptations.

Learning outcomes

• To know that gas exchange happens in the alveoli
• To be able to label a diagram of an alveolus
• To be able to describe the adaptations of the alveoli (with reasons)

Lesson steps

1. Introduction (20 mins)
   Ask students the following questions: Which gas enters and which one leaves the blood? Why is gas exchange necessary? Where does gas exchange happen in the lungs?
   Students test inhaled and exhaled air with lime water to see the difference (if they have not done this already). Include a risk / hazard assessment in accordance with the guidelines in your country.
   
   Introduce the words alveolus and alveoli, explain that this is where gas exchange happens and that they are going to go on an expedition into the lungs to learn about the alveoli in more detail.
   
2. Expedition (20 mins)
   Lead students through the expedition asking:
   
   Bronchioles:
   - Where are the bronchioles in the lungs?
   - What are the “sacs” at the end of the bronchioles called?
   - Why do these sacs have such a dense capillary network?
   Students add labels to their respiratory system diagram of the Lung structure Student Sheet, found in the Lesson resources section. Then answer the discussion questions from the expedition
   
   Inside the alveolus:
   - Name and describe two different types of cell in the alveolus. State their function.
   - State three adaptations of the alveolus.
   Students answer the discussion questions from the expedition.
3. Activity (20 mins)
   Go over answers to the discussion questions from the expedition with an emphasis on the adaptations of the alveoli.
   Alveolus colouring in activity (students may go back and visit either scene during this activity. They can also use this BBC Bitesize page to help.
   Students examine a floret of broccoli or cauliflower; explain that the structure is similar to that of the lungs.
   Students take a photo and label which parts of the broccoli represent parts of the lungs.
4. Extension
   Students research the mechanism of ventilation in order to prepare themselves for the next lesson.
   Students watch this higher-level flash animation showing gas exchange by MH Education and try the quiz.
   Students take the Khan Academy’s respiratory system quizzes:

• Introduction
• Intermediate
• Advanced

England

Key Stage 3/4 Science

• The structure and functions of the gas exchange system in humans, including adaptations to function
• The mechanism of breathing to move air in and out of the lungs, using a pressure model to explain the movement of gases, including simple measurements of lung volume
• The impact of exercise, asthma and smoking on the human gas exchange system