Blood on the tracks

A child's toy train set can make an excellent model for explaining the circulatory system to key stage 4 (Year 10) students. You will find that the wooden sets work best due to their versatility and the ease with which tracks of different designs can be constructed.

Laying out the track on the floor allows students to visualise the route taken by the blood as it flows around the body. The functions of the blood can be explained by loading and unloading the trucks of a train with oxygen, carbon dioxide, sugar and urea at the appropriate points.

Some students learn best by seeing things. Some learn best by hearing about things and talking them through. Others by physically interacting with their work and by acting things out. Every class will have a mixture of these types of learner. This activity meets the needs of all three: visual, auditory and kinaesthetic.

The kinaesthetic learners will love constructing a track that represents the heart, lungs, some of the other major body organs, and the main arteries and veins.

A good track requires a free floor space of about two metres by three metres. The heart will take up an area equivalent to two sheets of flipchart paper. Laying down the paper before you construct the track will allow you to draw and label the chambers of the heart, including the valves.

Visual learners will be able to see the dual circulation system in operation as the blood leaves the right side of the heart (ventricle), flows to the lungs, returns to the left atrium of the heart, leaves from the left ventricle, travels round the body and finally returns to the right atrium to start the cycle again.

Loading and unloading the train's trucks at the appropriate points with oxygen, carbon dioxide, sugar and urea (coloured "Molymod" beads are good for this) is kinaesthetic and highly visual.

A running commentary satisfies the auditory learners, ensuring that all learning preferences are well catered for. Students must take it in turns to describe what is happening... "The blood is now leaving the lungs flowing down the pulmonary vein toward the left atrium."

An object such as a small red bean bag (the red blood cell) can be passed from student to student allowing the speaker to nominate who in the group should pick up the story and continue the commentary. This device helps to keep students on their toes and allows the teacher to intervene at any point by calling for the bean bag and deciding who gets it next.

Once you have bought the track you will probably find that it is a very versatile resource. A decent train set could also be used to model the digestive system, the hormonal regulation of blood sugar, series and parallel circuits, and even the carbon cycle.

John Morrison teaches science at Easingwold school, north Yorkshire. Email:


Twenty straight track sections (various lengths), 20 curved track sections, 8 tight curve sections (small radius of curvature), 1 bridge, 1 locomotive with trucks.

When buying your track, don't forget to get a bridge or "fly-over" to allow the pulmonary vein to cross the aorta. Curved track sections come with different radii of curvature. You will need some tight curves to get the blood flowing in and out of the ventricles.

The original, brand-name wooden track is prohibitively expensive but if you shop around there are a number of inexpensive alternatives. Tesco does an own-label track that is reasonably priced.

The amount of track needed for this exercise would cost approximately Pounds 40. A battery-powered locomotive is about pound;6.

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