heart

• blood flow

  Body tissues ➔ vena cava ➔ right atrium ➔ right ventricle ➔ pulmonary artery ➔ lungs ➔ pulmonary vein ➔ left atrium ➔ left ventricle ➔ aorta ➔ body tissues
• Pacemaker cells are found in which chamber of the heart?

  right atrium
• Structure and function of arteries 5 points

  1. Arteries are large and carry blood at a very high pressure.
  2. Artery walls have a thick middle layer, containing both muscle and elastic tissue.
  3. The muscle tissue provides strength, and allows the arteries to direct blood flow.
  4. The elastic tissue allows the arteries to stretch and recoil.
  5. Compared to their walls, arteries have a relatively narrow lumen, which keeps the blood pressure high.
• Structure and function of capillaries 5 points

  • Capillaries are the smallest of the three blood vessels.
  • The role of capillaries is to exchange nutrients and waste products with the tissues.
  • Capillary walls are permeable, meaning substances are able to move through them.
  • Their walls are also only one cell thick which means a short distance for diffusion.
  • Capillaries carry blood at a low pressure and have a lower rate of flow than arteries.
• Structure and function of veins 5 points

  • The role of veins is to carry blood from the body (or lungs) back to the heart.
  • Veins are a similar size to arteries, but they have relatively thin walls and a relatively wide lumen
  • This is because they carry blood at a much lower pressure.
  • Veins also contain valves to prevent the blood from flowing backwards.