A vein in the forearm carries blood towards the heart at low pressure. A surrounding skeletal muscle contracts and squeezes the vein, but one valve in the vein is unable to close.
Explain the effect of the faulty valve on the return of blood to the heart when the muscle relaxes.
67 exam-style questions on Edexcel GCSE Biology 8.2 Blood and circulation, covering 8.2.1 Structure and function of the blood, 8.2.2 Structure of blood vessels, 8.2.3 Structure of the heart and circulatory system, and 8.2.4 Cardiac output. Each one has a worked solution and a mark scheme showing where the marks go.