Structure & Function of Blood Vessels: Extended (CIE IGCSE Biology)

Arteries

• Have thick muscular walls containing elastic fibres to withstand the high pressure of blood and maintain the blood pressure as it recoils after the blood has passed through
• Have a narrow lumen to maintain high pressure

Veins

• Have a large lumen as blood pressure is low
• Contain valves to prevent the backflow of blood as it is under low pressure

Capillaries

• Have walls that are one cell thick so that substances can easily diffuse in and out of them
• Have ‘leaky’ walls so that blood plasma can leak out and form tissue fluid surrounding cells

Adaptations of blood vessels

Arterioles and venules

• As arteries divide more as they get further away from the heart, they get narrower
• The narrow vessels that connect arteries to capillaries are called arterioles
• Veins also get narrower the further away they are from the heart
• The narrow vessels that connect capillaries to veins are called venules

The blood vessel network