Structure & function of blood vessels (WJEC A-level Biology)

This lesson describes how the structure of arteries, arterioles, capillaries, venules and veins in the mammalian circulatory system relate to their functions. The PowerPoint and accompanying resources are part of the second lesson in a series of 2 lessons which have been designed to cover specification point (b) of topic 3 in AS unit 2 of the WJEC A-level Biology A specification. The first lesson in this series covers the structure and function of the human heart and its associated blood vessels

This lesson has been written to build on any prior knowledge from GCSE or earlier in this topic to enable students to fully understand why a particular type of blood vessel has particular features. Students will be able to make the connection between the narrow lumen and elastic tissue in the walls of arteries and the need to maintain the high pressure of the blood. A quick version of the GUESS WHO game is used to introduce smooth muscle and collagen in the tunica media and externa and again the reason for their presence is explored and explained. Moving forwards, it is quite likely that some students will not be aware of the transition vessels that are the arterioles. This section begins with an understanding of the need for these vessels because the structural and functional differences between arteries and capillaries is too significant. The action of the smooth muscle in the walls of these vessels is discussed and students will be challenged to describe a number of situations that would require blood to be redistributed. The middle part of the lesson looks at the role of the capillaries in exchange and links are made to diffusion to ensure that students can explain how the red blood cells pressing against the endothelium results in a short diffusion distance. The remainder of the lesson considers the structure of the veins and students are challenged to explain how the differences to those observed in arteries is due to the lower blood pressure found in these vessels.