The Circulatory system

• The circulatory system has two main functions: Transport blood cells, food, carbon dioxide, and protection against disease
• Red blood cells

  • Transport oxygen and are adapted for this by containing haemoglobin that oxygen binds to
  • Biconcare shape gives a large surface area
  • Absence of a nucleus - can carry more haemoglobin
• White blood cells

  • Lymphocytes produce antibodies
  • Phagocytes engulf and digest microorganisms
• Platelets

  • Help convert fibrinogen to fibrin in blood clotting
  • The fibrin forms a mesh to trap the blood and in the formation of scabs
• Plasma

  Liquid part of blood; main function is transport of blood cells, food molecules, carbon dioxide, hormones and urea
• Salts and other chemicals in the plasma keep its concentration stable and at a concentration similar to that of the blood cells. This is important, because if red blood cells are placed in water they will take in water by osmosis and burst in a process called cell lysis
• Arteries

  • Blood flows away from the heart
  • Walls are thick, contain muscle for strength, and are elastic to allow arteries to expand and recoil as blood pulses through
  • High blood pressure
  • No valves
  • Relatively small lumen diameter
• Veins

  • Blood flows back to the heart
  • Thinner walls = less muscle and lower elastic levels
  • Low blood pressure
  • Has valves to prevent backflow of blood
  • Relatively large lumen diameter
• Capillaries


  • Blood flow from arteries to veins
  • Walls are one cell thick to allow exchange between the blood and body cells
  • Low blood pressure
  • No valves
  • Very small lumen diameter
• Pulmonary circulation

  Blood flow from the right ventricle to the lungs and back to the left atrium
• Systemic circulation

  Blood flow from the left ventricle to the body and back to the right atrium
• Heart

  • Pumps blood around the body
  • Has a double circulation - the blood travels through the heart twice for each complete circuit of the body
  • Ventricles are thicker than the atria as they are the chambers that pump
  • Left ventricle has a thicker muscular wall as it pumps blood around the body
  • Valves prevent backflow and make sure the heart acts as a unidirectional pump
  • Coronary blood vessels supply the heart muscle with blood
• Regular exercise

  • Strengthens the heart muscle
  • Increases cardiac output even when not exercising
  • Reduces recovery time - length of time taken for someone's pulse rate to return to normal after exercise
• Cardiac output

  The volume of blood pumped by the heart per minute
• Pulse rate

  How often a "pulse" or surge of blood passes round the body
• Heart rate

  How often the heart beats
• White Blood Cells 


  defence against disease
• Pulmonary Artery 


  carries deoxygenated blood to lungs
• Right Atrium 


  receives blood from body
• vena cava 


  returns blood to body
• right ventricle

  pumps blood to lungs
• left ventricle 


  pumps blood around the body
• valves 


  prevent backflow of blood
• left atrium 


  receives blood from lungs
• pulmonary vein


  returns oxygenated blood from lungs
• aorta 


  carries oxygenated blood at high pressure around body
• Ventricles 


  thicker than the atria as they are the chambers that pump blood
• Left Ventricle 


  Has thicker muscular wall as it pumps blood around the body
• Valves 


  make sure the heart acts as a unidirectional pump
• Coronary Blood Vessels

  supply heart muscle with the blood
• Recovery Time 


  length of time taken for someone’s pulse rate to return to normal after exercise
• Aorta 


  The main artery that carries blood under high pressure away from heart
• Left atrium 


  Heart chamber that receives blood from the lungs
• Left ventricle 


  The heart chamber that pumps blood around the body
• Pulmonary artery 


  Carries deoxygenated blood from heart to lungs
• Pulmonary vein 


  Carries oxygenated blood from lungs to heart
• Right atrium 


  Receives blood from vena cava
• Right ventricle 


  pumps blood to lungs
• Vena cava 


  Returns deoxygenated blood to the heart
• Pulmonary 


  Lungs