circulatory system

• Circulatory system


  The system that circulates blood around the body
• Components of the circulatory system

  • Plasma
  • Red blood cells
  • White blood cells
  • Platelets
• 3 main functions of the circulatory system

  • Transport
  • Protection
  • Other
• Plasma


  The liquid part of the blood, composed mostly of water, that acts as a medium for the other blood cells and contains dissolved nutrients
• Red blood cells


  • Made in bone marrow
  • Most common type of blood cell
  • Disc shaped
  • No nucleus
  • Very flexible
  • Contain haemoglobin to carry oxygen
• White blood cells


  • Less numerous than red blood cells
  • Have a nucleus but come in different shapes
  • Defend the body against disease and infections
• Platelets


  • Help clot the blood to prevent leaks
  • Stop bleeding
  • If someone cannot produce platelets they are a haemophiliac
• Blood vessels


  • Arteries
  • Veins
  • Capillaries
• Arteries


  • Always take blood away from the heart
  • Thick walled
  • Very elastic to expand under high pressure
• Veins


  • Thin walled
  • Not very elastic as blood is under low pressure
  • Have valves to prevent backwards flow
• Capillaries


  • Only 1 cell thick
  • Surround all our organs
  • Allow easy passage of gas and nutrients
• Blood vessel functions


  • Arteries - Carry blood towards the heart, have valves
  • Capillaries - Allow gas and nutrient exchange
• Heart


  The pump of the circulatory system, roughly the size of a clenched fist, beats around 70 times per minute
• Cardiac muscle


  • The type of muscle the heart is made of, which doesn't get tired
• Heart structure


  • 4 chambers - 2 atria and 2 ventricles, split by a septum
• Heart blood vessels


  • 2 bring blood to the heart (vena cava, pulmonary vein)
  • 2 bring blood away from the heart (aorta, pulmonary artery)
• Pathway of blood


  1. Deoxygenated blood arrives at vena cava

  2. Passes to right atrium to right ventricle

  3. Pumped to lungs via pulmonary artery

  4. Picks up oxygen in lungs

  5. Returns to heart via pulmonary vein

  6. From left atrium to left ventricle

  7. Pumped out aorta to body
• The left side of the heart is thicker
• Coronary arteries


  The arteries that supply the heart muscle with its own blood supply
• Double circulation


  The blood circulates through the lungs and then the body