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InkFlaskCambridge IGCSE
Contains the answers

Answers · Blood vessels

Blood vessels — return questions key

Check meaning, not exact wording. These are teaching points, not official Cambridge marks.

1. AR1 · Return

Model answer. Veins have valves along their length. The valves prevent the backflow of blood, so blood in a vein flows only towards the heart.

A full answer includes

  • Valves.
  • They prevent the backflow of blood.

Also accept

  • valves; prevent backflow

Watch for

  • “Veins have muscle in the wall, which arteries do not.” — Both have muscle in the wall; an artery has more. The feature found only in veins is valves.

2. AR2 · Return

Model answer. The elastic tissue in an artery's wall stretches when a surge of blood arrives and recoils between beats, so the flow becomes smoother.

A full answer includes

  • The elastic tissue in its wall.

Also accept

  • elastic tissue in the wall

Watch for

  • “The valves in the artery.” — Arteries have no valves along their length. The elastic tissue smooths the flow.

3. CR1 · Return

Model answer. A capillary has a wall one cell thick and a lumen about the width of one red blood cell.

A full answer includes

  • (1) one cell; (2) one red blood cell.

Also accept

  • (1) one cell; (2) one red blood cell

Watch for

  • “A capillary's wall is many cells thick, to protect the blood.” — The wall is a single layer of flattened cells, so substances can cross it quickly.

4. CR2 · Return

Model answer. Capillaries carry blood close to every cell and allow substances to be exchanged between the blood and the cells.

A full answer includes

  • Exchanging substances between the blood and the cells of a tissue.

Also accept

  • exchanging substances between the blood and the cells

Watch for

  • “Pumping blood back to the heart.” — Capillaries have no muscle. Veins carry the blood back; the heart pumps it.

5. CR3 · Return

Model answer. Many capillaries give a very large surface area across which substances can diffuse, and they run between the cells, so every cell is close to one and the diffusion distance is short.

A full answer includes

  • A large surface area for exchange.
  • Every cell is close to a capillary, so the diffusion distance is short.

Also accept

  • large surface area; every cell close to a capillary

Watch for

  • “Many capillaries make the blood pressure in the tissue higher.” — The benefit is a large surface area and short distances for diffusion.

6. MR1 · Return

Model answer. The vena cava brings deoxygenated blood from the body into the right side of the heart.

A full answer includes

  • The vena cava.

Also accept

  • the vena cava

Watch for

  • “The aorta.” — The aorta carries blood away from the heart to the body. The vena cava brings it back.

7. MR2 · Return

Model answer. The hepatic veins carry blood from the liver to the vena cava.

A full answer includes

  • The hepatic veins.

Also accept

  • hepatic veins

Watch for

  • “The hepatic portal vein.” — The hepatic portal vein brings blood into the liver from the gut. The hepatic veins take it away.