Blood Vessels (Cambridge (CIE) O Level Biology): Revision Note

Arteries, Veins & Capillaries

Arteries

• Carry blood at high pressure away from the heart

• Carry oxygenated blood (other than the pulmonary artery)

• Have thick muscular walls containing elastic fibres

• Have a narrow lumen

• The speed of flow is fast

Veins

• Carry blood at low pressure towards the heart

• Carry deoxygenated blood (other than the pulmonary vein)

• Have thin walls

• Have a large lumen

• Contain valves (to prevent the backflow of blood)

• The speed of flow is slow 

Comparison of Arteries and Veins Diagram

Comparing arteries and veins

Capillaries

• Carry blood at low pressure within tissues

• Carry both oxygenated and deoxygenated blood

• Have walls that are one cell thick

• Have ‘leaky’ walls

• In some capillaries, the lumen is only wide enough for red blood cells to pass through in single-file

• The speed of flow is slow

Structure of a capillary