Blood Vessels (Cambridge (CIE) IGCSE Combined Science: Biology): Revision Note

Arteries, veins & capillaries

• The blood vessels are a system of closed tubes within which blood flows

• Different types of blood vessels transport blood in different directions, and to different parts of the body

Arteries

• These blood vessels carry blood away from the heart at high pressure

• Arteries transport oxygenated blood

  • The single exception to this is the pulmonary artery

• The walls of arteries are thick and muscular and contain elastic fibres

• Arteries have a narrow lumen

Veins

• These blood vessels carry blood towards the heart at low pressure

• Veins transport deoxygenated blood

  • The single exception to this is the pulmonary vein

• The walls of veins are thin in comparison to arteries

• Veins have a wide lumen

• Valves in veins prevent blood from flowing backwards

Capillaries

• These blood vessels carry blood to the cells of the tissues

• Capillaries transport oxygenated blood from the arteries to the cells, and deoxygenated blood from the cells to the veins

• The walls of capillaries are one cell thick and contain gaps to allow fluid to leak out

• Capillaries have a very narrow lumen