Blood Vessels

• Which blood vessel has valves?

  Veins

  
• Why do veins have valves?

  To prevent backflow of blood into the heart.

  
• Arteries carry blood AWAY from the heart. have a smaller lumen. Thick cell walls to withstand high pressure, and Elastic walls to stretch and recoil.

  
• Capillaries exhange substances in our cell. They are permeable, so substances can easily diffuse.

  
• Veins carry blood TO the heart. Have a big lumen. They have Low blood pressure. They have valves.

  
• Why are the capillaries one cell thick?

  Short Diffusion Pathway, Making diffusion faster.