Blood vessels

• What is the main function of arteries?

  Carry blood away from the heart
• Why do arteries have thick walls?

  To withstand high pressure from the heart
• What is the lumen of an artery like?

  Small
• What materials make artery walls strong?

  Thick layers of muscle and elastic fibres
• Why do arteries have elastic fibres?

  To allow them to stretch
• What do capillaries branch from?

  Arteries
• How thick are capillary walls?

  One cell thick
• What is the size of capillaries?

  Really tiny, too small to see
• What do capillaries supply to cells?

  Food and oxygen
• What waste do capillaries remove from cells?

  Carbon dioxide (CO₂)
• Why do capillaries have permeable walls?

  To allow substances to diffuse in and out
• Why is it beneficial for capillary walls to be one cell thick?

  To allow quick substance exchange
• What do capillaries join to form?

  Veins
• How do the walls of veins compare to arteries?

  Thinner than artery walls
• Why do veins have a larger lumen than arteries?

  To help blood flow at low pressure
• What feature do veins have to prevent backflow?

  Valves
• How many miles of blood vessels are in the human body?

  About 60,000 miles
• How does the distance of blood vessels compare to London to Sydney?

  About six times that distance
• What are the main characteristics of arteries, capillaries, and veins?

  Arteries:

  • Thick walls
  • Small lumen
  • Strong and elastic
  • Carry blood away from the heart

  
  

  Capillaries:

  • One cell thick
  • Very small lumen
  • Supply food and oxygen
  • Remove waste like CO₂

  
  

  Veins:

  • Thinner walls than arteries
  • Larger lumen
  • Carry blood back to the heart
  • Have valves to prevent backflow