Blood vessels

• What is the primary function of blood vessels in the circulatory system?

  To carry blood around the body
• What are the three main types of blood vessels and their functions?

  • Arteries: carry blood away from the heart
  • Capillaries: allow easy exchange of materials at the tissues
  • Veins: carry blood to the heart
• How do arteries differ from veins in terms of blood pressure?

  Arteries carry blood under high pressure, while veins carry blood at lower pressure
• What structural features of arteries help them carry blood under pressure?

  Artery walls are strong, elastic, and thick
• Why do arteries have thick walls compared to their lumen?

  To withstand the high pressure of blood pumped from the heart
• What is the composition of artery walls?

  Thick layers of muscle and elastic fibres
• How thick are capillaries compared to other blood vessels?

  Capillaries are one cell thick
• What is the lumen of a capillary like?

  Capillaries have a very small lumen
• What is the significance of capillaries being permeable?

  It allows substances to get in and out easily
• What do capillaries supply and remove from tissues?

  They supply food and oxygen and remove waste like CO2
• How does the thickness of capillary walls affect diffusion?

  Thinner walls increase the rate of diffusion
• How do veins differ from arteries in structure and function?

  • Veins have thinner walls than arteries
  • Veins have a larger lumen than arteries
  • Veins contain valves to prevent backflow
  • Veins carry blood back to the heart at lower pressure
• What happens to capillaries as they converge?

  They join up to form veins
• Why do veins have a larger lumen than arteries?

  To help blood flow despite lower pressure
• What is the purpose of valves in veins?

  To help keep blood flowing in the right direction
• How do you calculate the rate of blood flow?

  Rate of blood flow = volume of blood ÷ number of minutes
• If 1464 ml of blood passed through an artery in 4.5 minutes, what is the rate of blood flow?

  The rate of blood flow is $325 \text{ ml/min}$
• If 2.175 litres of blood passed through a vein in 8.7 minutes, what is the rate of blood flow in ml/min?

  The rate of blood flow is $250 \text{ ml/min}$