Blood Vessels - Veins
Biology: AQA GCSE Higher, topic 2.3.4
Veins
Veins form when capillaries join up after passing through the body. They transport deoxygenated (contains no oxygen) blood (apart from the pulmonary vein) from the organs back to the heart. They are different to arteries because:
Thinner walls than arteries
- The walls are thinner than those found in the arteries as the blood is at a lower pressure.
Wider cross-section (lumen) than arteries
- Low pressure hinders blood flow. This means that veins have a wider cross-section through which blood can flow to counteract this.
Valves
- Veins have valves to prevent the backflow of blood.
Test yourself on Blood Vessels - Veins
Why do veins have valves?
What is unusual about the pulmonary vein compared with other veins?
Why do veins have a wider cross-section than arteries?
Why do artery walls contain thick layers of muscle, unlike vein walls?
Why can vein walls be thinner than artery walls?