- Review, using quick questions, pupils' understanding of the composition of air breathed into the lungs and the importance of oxygen for aerobic respiration. Ask pupils to suggest what happens to air when it enters the lungs. Establish,
eg using simulation software, that oxygen enters the blood and is transported elsewhere, and that carbon dioxide produced in the cells passes out of the blood.
- Show illustrations, models or animated pictures of the fine structure of the lungs and ask pupils to suggest why the alveoli have so many blood vessels around them. Provide information about carbon dioxide and oxygen concentrations in the blood. Ask pupils to predict what happens in the alveolus. Help pupils to annotate diagrams with arrows to show the direction of movement of oxygen and carbon dioxide and describe gas exchange in terms of a supply of oxygen to the blood and removal of carbon dioxide from the blood.
- Show illustrations of damaged lungs from,
eg emphysema, dust damage. Ask the pupils to describe the differences and predict what effects this damage may have on gas exchange.
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- describe features of the alveoli,
eg very thin walls, large surface area,
the network of blood capillaries around the alveoli
- describe the movement of gases from air to blood and blood to air
- describe how carbon dioxide and oxygen are exchanged at the surface of an alveolus
- describe how damaged lungs will result in less gas exchange
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