The heart, blood and vessels

• Circulatory system


  • Transports substances to supply cells and remove waste products
• Heart


  Muscular organ that pumps blood around the body
• Heart chambers


  • Right atrium
  • Left atrium
  • Right ventricle
  • Left ventricle
• Blood vessels


  • Arteries carry blood away from the heart
  • Veins carry blood to the heart
  • Capillaries connect arteries and veins
• Arteries


  Blood vessels that carry blood away from the heart
• Veins


  Blood vessels with valves that transport blood to the heart
• Capillaries


  Tiny blood vessels with walls one-cell thick where exchange of materials occurs
• Arteries


  • Always carry blood away from the heart
  • Carry oxygenated blood, except for the pulmonary artery
  • Carry blood under high pressure
  • Have thick muscular and elastic walls to pump and accommodate blood
  • Have a narrow lumen
• Veins


  • Always carry blood to the heart
  • Always carry deoxygenated blood, except for the pulmonary vein
  • Carry blood under low pressure
  • Have thin walls
  • Have a wide lumen
• Exchange of molecules across capillary walls


  Oxygen, Carbon dioxide, Glucose, Urea
• Valves


  Prevents blood flowing backwards.
• Right ventricle


  pumps blood to the lungs where gas exchange takes place.
• Left ventricle


  pumps blood around the rest of the body
• Natural resting heart rate

  controlled by a group of cells located in the right atrium that act as a pacemaker
• Capillaries

  • One cell thick walls so molecules can diffuse across
  • Tiny lumen
  • Carry materials under low pressure
• Name the components of the blood.

  • Red blood cells
  • White blood cells
  • Plasma
  • Platelets
• What are platelets?


  Small fragments of cells that are involved in blood clotting. Prevents the loss of blood and stops wounds becoming infected.
• What is plasma?


  A straw-coloured liquid that carries platelets, red and white blood cells, carbon dioxide, digested food including glucose, amino acids and soluble nutrients. It also carries urea, hormones, antibodies, antitoxins and proteins.
• Red blood cells

  • Transports oxygen around the body.
  • Binds to haemoglobin
  • Biconcave disc shape to maximise surface area for oxygen absorption
  • No nucleus
• White blood cell


  Ingesting pathogens and producing antibodies.

  • Phagocytes engulf and destroy unwanted microorganisms that enter the blood.
  • Lymphocytes produce antibodies
• What is the function of the coronary arteries?


  Supplies blood, and therefore oxygen, to the heart muscle.
• What is coronary heart disease?

  Layers of fatty material (caused by certain kinds of 'bad' cholesterol) build up inside the coronary arteries, narrowing them. This reduces the flow of blood through the coronary arteries, resulting in a lack of oxygen for the heart muscle.
• What are stents?


  Stents are small mesh tubes used to keep the coronary arteries open so blood can pass through to the heart.

  • Pro: Effective for a long time and quick recovery time.
  • Con: Risk of complications during surgery and risk of patient developing a blood clot near stent.
• What are statins?


  Drugs that can reduce the amount of 'bad' cholesterol present in the bloodstream.

  • Pros: Slows down the rate of fatty material deposit.
  • Cons: Must be taken regularly and can cause negative side effects e.g. kidney failure and memory loss.
• Faulty valves

  • Valves can be damaged or weakened by heart attacks, infection or old age. They may stiffen or become leaky.
  • Mechanical valves: Lasts a long time but requires medicine to prevent clotting.
  • Biological valves: Doesn't require medicine but only lasts 12 to 15 years.
• Artificial hearts


  Temporary fix to keep patient alive whilst waiting for a heart transplant, or to allow the heart to rest as an aid to recovery.