Arteries, Veins and Capillaries

• What type of circulatory system do humans have?

  Double circulatory system
• What is the primary function of arteries?

  Carry high pressure blood from the heart
• How do the thick muscular walls of arteries benefit their function?

  They withstand high pressure of blood
• What happens to blood in arteries with each heartbeat?

  Blood surges through the arteries
• What can be felt in the wrist as blood surges through arteries?

  The pulse
• What role do elastic fibers play in arteries?

  They stretch and recoil to maintain blood flow
• What are capillaries primarily involved in?

  Diffusion of substances
• Why do capillaries have very thin walls?

  To allow rapid diffusion of substances
• What substances diffuse from blood to cells in capillaries?

  Glucose and oxygen
• What substance diffuses from cells back to the blood?

  Carbon dioxide
• What happens to blood after it passes through the organs?

  It returns to the heart through veins
• Why do veins have thin walls?

  Because the blood pressure is low
• What do many veins contain to prevent backflow of blood?

  Valves
• How do valves in veins function?

  They open to allow forward flow and close to prevent backflow
• What happens when blood starts to flow backwards in veins?

  The valves close to stop the backflow
• How do the structures of arteries, veins, and capillaries relate to their functions?

  • Arteries: Thick muscular walls for high pressure
  • Veins: Thin walls and valves for low pressure
  • Capillaries: Thin walls for rapid diffusion
• What are the main functions of blood vessels in the circulatory system?

  • Arteries: Transport oxygenated blood away from the heart
  • Veins: Return deoxygenated blood to the heart
  • Capillaries: Facilitate exchange of substances