Circulation

• Functions of the Circulation System


  • Transport of gases and nutrients
  • Defence against disease
  • Clotting to prevent blood loss
• Double circulation


  Blood moves through a complete circuit of the body twice, through the heart
• Blood vessels


  • Tubes which carry blood around the body
• Artery


  Carries blood from the heart under high pressure
• Vein


  Carries blood into the heart under low pressure
• Veins


  Drain the blood back from the tissue to the heart at low pressure
• Veins


  Have thinner walls than arteries, and carry deoxygenated blood back to the heart
• Capillaries


  Are the smallest blood vessels, where gases are exchanged including oxygen, carbon dioxide and waste
• Characteristics of blood vessels

  • All have Lumen
  • All carry blood
  • All vessels
• Artery


  • Carries oxygenated blood away from the heart
  • Has thick walls and small lumen
• Vein


  • Carries deoxygenated blood towards the heart
  • Has thin walls and long lumen
  • Has valves to prevent backflow
• Capillary


  • Smallest blood vessel
  • Walls are one cell thick
  • Site of gas exchange
• Red blood cells have a biconcave shape which provides a large surface area for absorbing oxygen quickly
• Red blood cells contain haemoglobin which transports oxygen by binding to form oxyhaemoglobin
• White blood cells


  • Phagocytes Have a lobed nucleus and lymphocytes have a large nucleus
  • phagocytes defend the body by engulfing and digesting foreign materials
  • Lymphocytes produce antibodies to stick to and destroy microbes
• Platelets


  Fragments of cells involved in blood clotting
• Plasma


  • Liquid part of blood consisting mainly of water
  • Carries dissolved substances like glucose, antibodies and hormones
  • Also carries blood cells
• Circulatory system


  Carries blood to different areas of the body
• Heart


  Pumps blood
• The heart has 4 chambers - two upper (atria) and two lower (ventricles)
• Blood vessels


  • Arteries
  • Veins
  • Capillaries
• Blood flow in arteries

  Away from the heart
• Blood flow in veins


  Towards the heart
• Valves in veins and heart


  Prevent backflow of blood
• Investigating heart rate


  1. Rest for 5 minutes

  2. Record pulse 3 times

  3. Exercise for 1 minute

  4. Record pulse 3 times
• Fitness level


  Affects how much heart rate increases with exercise and how quickly it returns to normal
• Fitter people have a better circulating blood supply and lower risk of heart disease
• Heart disease


  • Build up of fatty deposits in coronary arteries
  • Heart attack occurs when an atheroma blocks blood flow to heart muscle
• Causes of heart disease


  • Smoking
  • Fatty diet
  • Lack of exercise
  • High salt diet
• Deoxygenated blood enters the right atrium through the superior vena cava or inferior vena cava.
• Blood flows from the right side to the left side of the heart.
• The pulmonary arteries send deoxygenated blood to lungs to pick up oxygen
• The pulmonary vein carries oxygenated blood to heart from lungs
• The oxygenated blood leaves to the rest of the body through the aorta
• Heart circulation

  
• Coronary artery disease is caused by fatty deposits on the walls of the arteries, which can cause them to narrow and restrict blood flow to the heart muscle
• The coronary artery supplies blood to the heart muscle itself