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The main blood vessels

Transport in animals · Blood vessels · note 2 of 2

Spec 9.3.3, 9.3.6Download all Blood vessels notes (PDF)Download all notes (PDF)5 pages

The main blood vesselsSpec 9.3.3, 9.3.6

In short

The main blood vessels are the vena cava, which brings deoxygenated blood from the body to the right atrium, the pulmonary artery to the lungs, the pulmonary vein back to the left atrium, and the aorta to the body. The renal artery and vein serve the kidneys, and the hepatic portal vein carries absorbed nutrients to the liver.

Main blood vessels
VesselCarries bloodOxygen content
Vena cavaFrom the body to the right atriumDeoxygenated
Pulmonary arteryFrom the right ventricle to the lungsDeoxygenated
Pulmonary veinFrom the lungs to the left atriumOxygenated
AortaFrom the left ventricle to the bodyOxygenated
Renal arteryFrom the aorta to the kidneyOxygenated
Renal veinFrom the kidney to the vena cavaDeoxygenated; contains less urea than the blood in the renal artery
Supplement (what this means)Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels mean

Blood vessels of the liver

Supplement (what this means)Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels mean
  • Hepatic artery: brings oxygenated blood to the liver.
  • Hepatic portal vein: brings blood from the small intestine, carrying absorbed nutrients, to the liver.
  • Hepatic veins: take blood away from the liver to the vena cava.
A plan of the circulation: the pulmonary artery takes blood from the right side of the heart to the lungs and the pulmonary vein returns it to the left side; the aorta carries blood to the body, with the hepatic artery to the liver and the renal artery to the kidneys; the hepatic portal vein carries blood from the small intestine to the liver; the hepatic vein and renal vein drain into the vena cava, which returns blood to the right side of the heart. Oxygenated blood is red and deoxygenated blood is blue. (opens full size in a new tab)
The main blood vessels. The hepatic artery, hepatic portal vein and hepatic vein are Supplement content.
Common mistake:

Arteries do not always carry oxygenated blood. The pulmonary artery carries deoxygenated blood and the pulmonary vein carries oxygenated blood. Artery or vein depends on the direction relative to the heart.

Quick check

  1. Which blood vessels have valves?

    Show answer

    Veins.

  2. State the function of capillaries.

    Show answer

    Exchange of substances between the blood and the cells of the body tissues.

  3. Supplement Why do arteries have thick walls?

    Show answer

    They carry blood at high pressure, so the walls must withstand it.

  4. Name the blood vessel that carries blood from the lungs to the heart.

    Show answer

    Pulmonary vein.

  5. Supplement Which vessel carries blood from the small intestine to the liver?

    Show answer

    The hepatic portal vein.

Written and checked against the Cambridge IGCSE Biology (0610) specification · Updated October 2026

Frequently asked questions

Why do arteries have thick elastic walls?

Supplement Arteries have thick walls containing muscle and elastic fibres because they carry blood away from the heart at high pressure. The thick walls withstand the pressure, and the elastic fibres let the walls stretch and recoil with each heartbeat. The narrow lumen helps to maintain the pressure as the blood travels to the organs.

Why do veins have valves but arteries do not?

Supplement Veins have valves because they carry blood back to the heart at low pressure, and the valves stop the blood flowing backwards. Arteries carry blood away from the heart at high pressure and do not have valves. Veins also have thin walls and a wide lumen, giving little resistance to flow.

What blood vessels carry blood away from the heart?

Arteries carry blood away from the heart, and veins return it to the heart. The aorta carries oxygenated blood from the left ventricle to the body, and the pulmonary artery carries deoxygenated blood from the right ventricle to the lungs. Arteries do not always carry oxygenated blood: the name depends on direction.

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