2.11 - Circulatory System (Blood Vessels)

• What do arteries carry at a very high pressure?

  Blood
• What is the composition of artery walls?

  Thick middle layer of muscle and elastic tissue
• What is the function of muscle tissue in arteries?

  Provides strength and directs blood flow
• How does elastic tissue benefit arteries?

  Allows arteries to stretch and recoil
• Why do arteries have a relatively narrow lumen?

  To keep the blood pressure high
• What are the key structural features of arteries?

  • Large size
  • Thick middle layer
  • Muscle and elastic tissue
  • Relatively narrow lumen
• What are the smallest blood vessels called?

  Capillaries
• What is the primary role of capillaries?

  To exchange nutrients and waste products
• What does it mean that capillary walls are permeable?

  Substances can move through them
• How thick are capillary walls?

  One cell thick
• Why is the thickness of capillary walls significant?

  It allows for a short distance for diffusion
• What type of blood pressure do capillaries carry blood at?

  Low pressure
• How does the flow rate of blood in capillaries compare to arteries?

  It has a lower rate of flow
• What are the key structural features of capillaries that facilitate their function?

  • Smallest blood vessels
  • Permeable walls
  • One cell thick
  • Low blood pressure
  • Lower flow rate than arteries
• What is the primary role of veins?

  To carry blood back to the heart
• How do the sizes of veins compare to arteries?

  Veins are similar in size to arteries
• What is a key structural difference between veins and arteries?

  Veins have thinner walls than arteries
• What is the lumen size of veins compared to arteries?

  Veins have a relatively wide lumen
• Why do veins carry blood at a lower pressure?

  Because they return blood to the heart
• What do veins contain to prevent backflow of blood?

  Valves
• What are the main structural features of veins?

  • Thin walls
  • Wide lumen
  • Valves to prevent backflow