CIE IGCSE Biology: 复习笔记:9.1.12 Structure & Function of Blood Vessels: Extended

CIE IGCSE Biology: 复习笔记:9.1.12 Structure & Function of Blood Vessels: Extended

How Structure of Blood Vessels is Adapted to their Function: Extended

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

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