The table describes three blood vessels.
Table
| Vessel | Wall | Lumen | Valves within the vessel |
|---|---|---|---|
| P | thick, with much muscle and elastic tissue | relatively narrow | absent |
| Q | one cell thick | very narrow | absent |
| R | thin, with little muscle and elastic tissue | wide | present |
Which sequence follows blood from the left ventricle through an organ and back towards the heart?
P →\rightarrow→ R →\rightarrow→ Q
P →\rightarrow→ Q →\rightarrow→ R
R →\rightarrow→ Q →\rightarrow→ P
Q →\rightarrow→ P →\rightarrow→ R
42 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.