Structure & Function of Blood Vessels (Cambridge International IGCSE Biology)

How structure of blood vessels is adapted to their function: Extended

Spec point — Explain how the structure of arteries and veins is related to the pressure of the blood that they transport Explain how the structure of capillaries is related to their functions

How structure of blood vessels is adapted to their function: Extended

Extended Tier Only

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