Circulatory System

• Arteries


  Carry blood away from the heart
• Arteries


  • High walls are thick
  • Blood is at high pressure so walls are strong and elastic
  • Thick layers of muscle, elastic fibers to allow them to stretch and snap back
• Capillaries


  • Arteries branch into capillaries
  • Are really small
  • Supply food and oxygen, taking away waste like CO2
  • Walls are thin to increase the rate of diffusion
• Blood flow


  1. Blood flows from veins to the right atrium

  2. Muscles in the right atrium contract to produce electrical impulses

  3. Ventricles contract, blood leaves the heart through the aorta and pulmonary artery

  4. Blood flows to organs through arteries and returns through veins
• Veins


  • Take blood back to the heart
  • Blood is at low pressure so the walls don't need to be as thick
  • Have a larger lumen to help blood flow
  • Have valves to keep blood flowing in the right direction
• The heart has 4 chambers
• In the right atrium, electrical impulses are produced to make the muscles contract
• Veins contract to push blood in the right direction