Contains the full lesson along with a supporting toolkit, including teachers’ notes.
The cardiovascular system
In the human body blood is pumped by the heart through blood vessels that range in diameter from about 1 cm down to less than a thousandth of that (0.01 mm or 10 μm). The blood transports nutrients and oxygen to body tissues and carries away carbon dioxide and other by-products of the body’smetabolism. The blood, the heart and the associated blood vessels are collectively known as the cardiovascular system.
The circulatory system
The circulatory system includes the cardiovascular system (the blood system) and the lymphatic system – a system of ducts and nodes containing lymph fluid. The nodes are small roughly kidney-shaped swellings, typically about 5 mm in diameter, where a number of lymph ducts meet. Lymph fluid is comparatively clear and does not contain red blood cells. It circulates more slowly than blood. The lymphatic system removes excess fluid from body tissues and has an important role in the body’s defence against disease.
The blood vessels that carry blood away from the heart are called arteries; they have thick walls and can withstand the relatively high pressure (about a sixth of atmospheric pressure). The vessels that carry blood back to the heart have relatively thin walls. The smallest blood vessels (the capillaries) are so small that red blood cells can just about squeeze through them.