Skip to content
InkFlaskCambridge IGCSE
Contains the answers

Answers · Blood vessels

Blood vessels — final check key

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

1. AK1 · Final check

Model answer. An artery has a thick wall, with a thick layer of muscle and elastic tissue, and a narrow lumen; it has no valves along its length. A vein has a thin wall and a wide lumen, and it has valves.

A full answer includes

  • Artery: thick wall (with muscle and elastic tissue), narrow lumen, no valves along its length.
  • Vein: thin wall, wide lumen, valves present.

Also accept

  • artery: thick wall, narrow lumen, no valves; vein: thin wall, wide lumen, valves

Watch for

  • “A vein has a thick wall to hold more blood.” — A vein holds more blood because of its wide lumen; its wall is thin.

2. AK2 · Final check

Model answer. Arteries carry blood at high pressure from the heart: their thick wall withstands the pressure, and the elastic tissue in it stretches with each surge and recoils between beats, smoothing the flow. Veins carry blood at low pressure: their thin wall is enough, their wide lumen lets the blood flow easily, and their valves prevent backflow while the squeezing of nearby muscles pushes the blood towards the heart.

A full answer includes

  • Arteries carry blood at high pressure: the thick wall withstands it; the elastic tissue stretches and recoils, smoothing the flow.
  • Veins carry blood at low pressure: a thin wall is enough and the wide lumen lets the blood flow easily; valves prevent backflow (and muscle contractions help return the blood).

Also accept

  • arteries: high pressure → thick, elastic wall; veins: low pressure → thin wall, wide lumen, valves

Watch for

  • “Arteries have thick walls because they carry more oxygen.” — The wall is related to pressure, not to oxygen: the pulmonary artery has a thick wall but carries deoxygenated blood.

3. CK1 · Final check

Model answer. (a) A capillary's wall is a single layer of flattened cells, one cell thick, and its lumen is very narrow, about the width of one red blood cell. (b) Capillaries carry blood from the arteries to the veins, close to every cell, and allow substances to be exchanged between the blood and the cells.

A full answer includes

  • (a) Wall one cell thick (no muscle); lumen narrow, about one red blood cell wide.
  • (b) Carry blood close to every cell, from arteries to veins; allow exchange of substances (oxygen and glucose out, carbon dioxide in).

Also accept

  • (a) wall one cell thick, narrow lumen; (b) carry blood close to cells; exchange

Watch for

  • “Capillaries have valves to keep the blood moving.” — Capillaries have no valves; only veins do.

4. CK2 · Final check

Model answer. The wall is one cell thick, so the diffusion distance is short and exchange is fast. The narrow lumen keeps the red blood cells in single file close to the wall. There are very many capillaries, giving a large surface area and keeping every cell close to one; the blood moves slowly through so many of them, which gives more time for exchange.

A full answer includes

  • Wall one cell thick: short diffusion distance, fast exchange.
  • Narrow lumen: red blood cells in single file, close to the wall.
  • Many capillaries: large surface area; every cell close to one.

Also accept

  • three of: thin wall → short distance; narrow lumen → cells close to the wall; many → large area, every cell close

Watch for

  • “A capillary's thick wall protects it from the pressure.” — The pressure in capillaries is low, and the wall is one cell thick: it is built for exchange, not strength.

5. MK1 · Final check

Model answer. (a) The aorta carries blood from the left side of the heart to the body. (b) The pulmonary vein brings oxygenated blood from the lungs. (c) The renal artery takes blood to a kidney, and (d) the renal vein takes it away.

A full answer includes

  • (a) aorta; (b) pulmonary vein; (c) renal artery; (d) renal vein.

Also accept

  • (a) aorta; (b) pulmonary vein; (c) renal artery; (d) renal vein

Watch for

  • “(b) The pulmonary artery.” — The pulmonary artery takes blood to the lungs. Blood comes back from the lungs in the pulmonary vein.

6. MK2 · Final check

Model answer. The hepatic artery brings oxygenated blood from the aorta. The hepatic portal vein brings blood from the stomach and small intestine. The hepatic veins take blood from the liver to the vena cava.

A full answer includes

  • Hepatic artery: from the aorta to the liver.
  • Hepatic portal vein: from the stomach and small intestine to the liver.
  • Hepatic veins: from the liver to the vena cava.

Also accept

  • hepatic artery (from the aorta); hepatic portal vein (from the gut); hepatic veins (to the vena cava)

Watch for

  • “The hepatic portal vein carries blood from the liver to the heart.” — It carries blood into the liver, from the gut. The hepatic veins carry blood out.