Topic 3
Blood vessels
Coursebook section 9.3 Teaching ideas ◆
Show students micrographs of transverse sections of an artery and a vein. (You should be able to find suitable images on the Internet.) Ask them to tell you the differences they can see between them, and build up a comparison table on the board. Follow this with a discussion of the functions of arteries and veins. ◆ If students are studying the Supplement, ask them to suggest links between the structures and functions of arteries and veins. ◆ Discuss the structure and function of capillaries, emphasising their tiny size compared with arteries and veins. Show students micrographs of capillaries in tissues. ◆ Display a large image of a diagram such as that in Figure 9.17 or 9.18, and discuss the names of the vessels supplying the different organs. Using Figure 9.17, ask students to work out how blood could get from one point in the body to another – they can think of the circulatory system as being like a one-way traffic system in a town. Common misunderstandings and misconceptions ◆
It is very common for students to think that arteries have to have thick walls because they are carrying oxygenated blood. They may think that oxygenated blood has a higher pressure than deoxygenated blood.
Homework ideas ◆ ◆ ◆
Coursebook questions 9.20 to 9.26 End-of-chapter questions 1, 2 and 4 Worksheet 9.2 Blood vessels
Topic 4
Blood
Coursebook section 9.4 Teaching ideas ◆
Ask students to look at blood vessels near the surface of the skin in their wrists or hands. (These may not be visible in all students, depending on skin colour, so take care not to offend.) They should be able to see that the blood in the very thin-walled vessel looks blue. Tell them the vessels they are looking at are veins, and discuss why the blood looks blue, and why it looks red if they cut themselves (the haemoglobin quickly combines with oxygen in the air to become bright red oxyhaemoglobin). ◆ Show students slides or micrographs of blood films, and help them to pick out red cells, white cells, platelets and plasma. They may be surprised to find out that the only red part of blood is the red cells, and that plasma is straw-coloured. Note: it is now against health and safety regulations in most countries for students to observe their own fresh blood, or blood from another source. ◆ If suitable images can be found, ask students to make a list of the differences in appearance of red blood cells and white blood cells. ◆ Discuss the functions of red blood cells in oxygen transport, platelets in clotting, white cells in the immune response and plasma in the transport of dissolved substances and heat. Original material © Cambridge University Press 2014 © Cambridge University Press 2014
IGCSE Biology
Chapter 9: Teaching ideas
3