Scheme of Work Cambridge International as & a level

9.1.2 Describe the distribution in the gas exchange system of cartilage, ciliated epithelium, goblet cells, squamous epithelium of alveoli, smooth muscle and capillaries.

9.1.3 Recognise cartilage, ciliated epithelium, goblet cells, squamous epithelium of alveoli, smooth muscle and capillaries in microscope slides, photomicrographs and electron micrographs.

9.1.4 Recognise trachea, bronchi, bronchioles and alveoli in microscope slides, photomicrographs and electron micrographs and make plan diagrams of transverse sections of the walls of the trachea and bronchus.

9.1.5 Describe the functions of ciliated epithelial cells, goblet cells and mucous glands in maintaining the health of the gas exchange system.

9.1.6 Describe the functions in the gas exchange system of cartilage, smooth muscle, elastic fibres and squamous epithelium.

9.1.7 Describe gas exchange between air in the alveoli and blood in the capillaries.

Learners observe prepared slides (or print-outs of photomicrographs and electron micrographs) of transverse and longitudinal sections of the wall of the trachea, bronchi, bronchioles and alveoli. Learners draw tissue maps and compare the features. Help learners to recognise ciliated epithelium, goblet cells, squamous epithelium of alveoli, smooth muscle and capillaries.

Sources of histology sections:

Learners describe the pathway of an oxygen molecule through the human gas exchange system, from the trachea and into the red blood cells where it binds to haemoglobin. Animations can help to provide further guidance, e.g. www.johnwiley.net.au/highered/interactions/media/Respiration/content/Respiration/resp1a/frameset.htm (I)

Display a challenging, 3–4-mark question on the whiteboard. Allow learners 2–3 minutes to work in pairs to record as many key terms they feel are necessary to answer it. Show how to incorporate the relevant key words into a clear, exam-style answer.

Host a lively class debate to motivate learners with higher-order thinking. The focus should be a controversial statement, rather than a question. For example, ask learners to evaluate a statement such as ‘The gas exchange system is more vital to humans than the circulatory system.’ (F)

Draw a very large diagram of the gas exchange system on the whiteboard. However, ensure that between five and ten mistakes have been intentionally included. These include spelling mistakes, but also conceptual errors. For example, show cilia in the alveoli, and cartilage rings around the bronchioles. The ‘think, pair, share’ technique can provide a useful introduction to help learners form an opinion. (F)