A vein carries blood from the scalp towards the heart.
Which statement explains why the wall of this vein is thin?
The thin wall provides the short diffusion distance needed for capillary exchange.
The blood is deoxygenated, so the wall needs less muscle to move it along.
The blood pressure is high, so the wall needs to stretch and recoil between heartbeats.
The blood pressure is low, so the wall does not need to withstand arterial pressure.
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.