Circulatory System

• The heart pumps blood and substances around the body

  In blood vessels
• The circulatory system

  Carries blood and dissolved substances to and from different places in the body
• The heart

  Pumps blood and substances around the body
• Components of the circulatory system

  • The heart
  • Blood vessels
  • Blood
• Delivering hormones

  To tissues
• Right side of the system

  • Deals with deoxygenated blood
• Circulatory system


  • Consists of 2 fully enclosed circuits
• Pulmonary circulation


  Carries blood from the heart to the lungs and back
• Left side of the system

  • Deals with oxygenated blood
• Circulatory system

  Humans have a double circulatory system, meaning it has two parts
• Systemic circulation


  Carries blood from the heart to all parts of the body and back
• Coronary arteries


  The hearts own blood supply
• Blood from the heart gets around the body with blood vessels
• Dub

  Shutting of the Aortic and Pulmonary valves to stop blood coming back into the ventricles
• The heart beats at around 60 to 80 times a minute
• The Lub-Dub sound of the heart beat is a result of the valves snapping shut
• Lub

  Contraction of the ventricles (A-V valves)
• How the heart works

  1. Blood from the body and lungs enters the heart

  2. The heartbeat begins when the heart muscles relax and blood flows into the aorta

  3. The aorta then contract and the valves open to allow blood into the ventricles

  4. The valves close to stop blood flowing backwards

  5. The ventricles contract forcing the blood to leave the heart

  6. At the same time the aorta are relaxing again and filling with blood

  7. This is how the cycle repeats itself
• Arteries

  • Elastic fibres allow the artery to stretch under pressure
  • Thick muscles contract to push blood along
• Arterioles


  Smaller branches of arteries
• Aorta


  Largest artery in the body
• Arteries


  Carry blood away from the heart
• Veins

  • Have valves which act to stop the blood from going in the wrong direction
  • Body muscles surround the veins so that when they contract to move the body, they also squeeze the veins and push blood across the vessel
• Vena Cava


  The largest vein in the body
• Veins and Venules


  Carry blood towards the heart
• Capillaries


  Link arteries with veins
• Exchange of materials

  Between the blood and other body cells
• The exchange of materials between the blood and the body can only occur through capillaries
• Capillary wall


  Is one cell thick
• Capillaries are the only site for the exchange of materials between the blood and the body
• Components of blood


  • Digested food
  • Red blood cells
  • White blood cells
  • Oxygen
  • Carbon dioxide
  • Plasma
  • Hormones
  • Platelets
  • Waste (urea)
• Humans have about 4-5 litres of blood in their body. This makes up roughly 8% of our bodyweight
• White blood cells


  • Lymphocytes
  • Macrophages
• Macrophages


  Eat and digest micro-organisms
• Some lymphocytes


  Fight disease by making anti-bodies to destroy invaders by dissolving them
• Other lymphocytes


  Make anti-toxins to break down poisons
• Platelets


  Bits of cell broken off from larger cells
• Activation of platelets


  Form a clot when they encounter collagen as a result of a break in the blood vessel
• The blood clot is like a net or plug</b>
• Blood clot formation


  Helps to prevent further bleeding