Identify Blood Vessels: Skills (HL IB Biology)

Distinguishing arteries and veins in micrographs

• Arteries
  • The arterial walls are much thicker and stronger than those of veins
    • This is due to the presence of more collagen and elastic fibres, as well as a thicker layer of smooth muscle
  • The lumen of arteries is relatively narrow compared to the thickness of the wall
    • This maintains the blood pressure inside the arteries
• Veins
  • The walls of veins are much thinner than those of arteries
    • They do not need to withstand the high pressure present in arteries
  • The lumen of veins is much wider in diameter compared to the thickness of the wall
    • A larger lumen helps to ensure that blood returns to the heart at an adequate speed
      • A large lumen reduces friction between the blood and the endothelial layer of the vein
      • The rate of blood flow is slower in veins but a larger lumen means the volume of blood delivered per unit of time is equal
• These characteristics can be used to distinguish arteries and veins in micrographs

Artery and vein micrograph diagrams

Arteries and veins can be distinguished from each other by the thickness of their walls and the diameter of the lumen; arteries (left) have thick walls and a narrow lumen while veins (right) have thin walls and a wide lumen

Note that you do not need to know the scientific names for the different tissue layers in the walls of the blood vessels