2.2.2 The Heart & Blood Vessels

• rate of blood flow = volume of blood / number of minutes
• What path does blood take around the body?

  Body tissues ➔ vena cava ➔ right atrium ➔ right ventricle ➔ pulmonary artery ➔ lungs ➔ pulmonary vein ➔ left atrium ➔ left ventricle ➔ aorta ➔ body tissues
• Where are pacemaker cells found?

  The right atrium.
• On each side of the heart, the atrium and ventricle are separated by a valve, which prevents the blood from flowing backwards.
• The _______ ventricle has thicker walls because it has to pump blood all the way around the body.

  Left
• Which blood vessel carries deoxygenated blood from the heart to the lungs?

  Pulmonary artery.
• Which blood vessel carries oxygenated blood from the heart to the body?

  Aorta.
• The movement of blood between the ventricles and atria: 

  1. The walls of the atria contract, pushing blood into the relaxed ventricles.
  2. The walls of the ventricles contract, pushing blood out of the heart. At the same time, more blood will enter the now-relaxed atria.
  3. The cycle repeats.
• Structure and function of arteries 

  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 

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

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

  Electrical devices used to correct heart rate irregularities.
• How are the lungs adapted for gaseous exchange?

  The lungs contain millions of air sacs called alveoli, which are where gas exchange occurs.
• What is the trachea?

  The trachea is the tube that allows air to pass in and out of the lungs.
• What is the bronchi?

  The two tubes which connect to each lung from the trachea.
• Breaths per minute = number of breaths / number of minutes