I find starting with this stripped back version of the heart is the best place to start when teaching this topic. Students can see the way blood will flow through by looking at the valves, they can then see the left side is thicker and work out blood must therefore be going round the body. This allows a slow build up of knowledge without being overwhelmed by a diagram with lines and labels everywhere.

Colourful, clear and comprehensive mind map designed to give an easy overview of knowledge required for the AQA A Level Biology course