Functions of the blood. pg 37-41

• Blood has 4 main components:

  1. Plasma.
  2. Platelets.
  3. Red blood cells.
  4. White blood cells.
• Plasma is a pale yellow liquid which carries things that need transporting around your body:

  1. Red and white blood cells and platelets.
  2. Digested food products from the gut to all body cells.
  3. Carbon dioxide from the body cells to the lungs.
  4. Urea from the liver to the kidneys.
  5. Hormones, which act as chemical messengers.
  6. Heat energy.
• Platelets are small fragments of cells that help blood clot.
• In a clot, platelets are held together by a mesh of a protein called fibrin.
• Red blood cells transport oxygen from the lungs to all the cells in the body.
• Adaptations of red blood cells:

  1. Small and biconcave shape to give a large surface area for absorbing and releasing oxygen.
  2. They contain haemoglobin, which contains a lot of iron.
  3. Lack of nucleus - this frees up space for more haemoglobin, so they can carry more oxygen.
• In the lungs, haemoglobin reacts with oxygen to become oxyhaemoblogin. In body tissues the reverse reaction happens to release oxygen to the cells.
• The immune system and white blood cells destroy pathogens.
• There are two different types of white blood cells: phagocytes and lymphocytes.
• Phagocytes ingest pathogens. They detect things that are 'foreign' to the body and then engulf and digest them. They are non-specific - they attack anything that's not meant to be there.
• Lymphocytes produce antibodies.
• Every pathogen has unique molecules (called antigens) on its surface.
• When lymphocytes come across a foreign antigen, they will start to produce proteins called antibodies. These lock onto the pathogens and mark them out for destruction by other white blood cells. These are produced rapidly and flow round the body to mark all similar pathogens.
• The antibodies produced by lymphocytes are specific to the type of antigen.
• Memory cells are produced in response to a foreign antigen. These remain in the body and remember a specific antigen. They can reproduce very fast if the same antigen enters the body again.
• Vaccination usually involves injecting dead or inactive pathogens into the body. These carry antigens, so even though they're harmless they still trigger an immune response - your lymphocytes produce antibodies to attack them. Memory cells will also be produced.
• There are 3 different types of blood vessels:

  1. Arteries.
  2. Capillaries.
  3. Veins.
• Arteries carry the blood away from the heart.
• Capillaries are involved in the exchange of materials at the tissues.
• Veins carry the blood to the heart.
• Arteries carry blood under pressure:

  1. The heart pumps the blood out at high pressure so the artery walls are strong and elastic.
  2. The elastic fibres allow arteries to expand.
  3. The walls are thick compared to the size of the lumen. They contain thick layers of muscles to make them strong.
  4. The largest artery in the body is the aorta.
• Capillaries:

  1. Arteries branch into capillaries.
  2. They're very tiny.
  3. They carry blood really close to every cell in the body to exchange substances with them.
  4. They have permeable walls, so substances can diffuse in and out.
  5. They supply food and oxygen, and take away wastes like CO2.
  6. Their walls are one cell thick. This increase the rate of diffusion by decreasing the distance over which it happens.
• Veins:

  1. Capillaries eventually join up to form veins.
  2. The blood is at lower pressure in the veins so the walls don't need to be as thick as artery walls.
  3. They have a bigger lumen than arteries to help the blood flow despite the lower pressure.
  4. They have valves to help keep the blood flowing in the right direction.
  5. The largest vein in the body is the vena cava.
• Diagram of the heart:

  A) right side

  B) left side

  C) pulmonary artery

  D) vena cava

  E) semi-lunar valve

  F) tricuspid valve

  G) right ventricle

  H) aorta

  I) pulmonary vein

  J) semi-lunar valveç

  K) bicuspid valve

  L) left ventricle

  
• Movement of blood in the heart:

  1. The right atrium receives deoxygenated blood from the body through the vena cava.
  2. The deoxygenated blood moves to the right ventricle, which pumps it to the lungs through the pulmonary artery.
  3. The left atrium receives oxygenated blood from the lungs through the pulmonary vein.
  4. The oxygenated blood moves to the left ventricle, which pumps it out round the whole body via the aorta.
• The left ventricle has a much thicker wall than the right ventricle. It needs more muscle to pump the blood around the whole body, whereas the right ventricle only needs to pump blood to the lungs.
• Blood in the left ventricle is under higher pressure than the blood in the right ventricle.
• The valves in the heart prevent the backflow of blood.
• When you exercise, your muscles need more energy, so you respire more.
• When exercising your heart rate increases:

  • Exercise increases the amount of carbon dioxide in the blood.
  • High levels of blood CO2 are detected by receptors in the aorta and carotid artery.
  • The receptors send signals to the brain.
  • The brain sends signals to the heart, causing it to contract more frequently and with more force.
• When an organism is threatened, the adrenal glands release adrenaline.
• Adrenaline binds to specific receptors in the heart. This causes the cardiac muscle to contract more frequently and with more force, so heart rate increases and the heart pumps more blood. This increases oxygen supply to the tissues.
• Circulation system structure:

  A) brain

  B) lungs

  C) heart

  D) liver

  E) gut

  F) kidneys

  G) pulmonary artery

  H) vena cava

  I) hepatic vein

  J) renal vein

  K) aorta

  L) pulmonary vein

  M) hepatic artery

  N) hepatic portal vein

  O) renal artery

  P) from lower limbs

  Q) to lower limbs

  
• Normally, arteries carry oxygenated blood and veins carry deoxygenated blood. The pulmonary artery and pulmonary vein are exceptions to this rule.
• 'Pulmonary' means to do with the lungs.
• 'Hepatic' means to do with the liver.
• 'Renal' means to do with the kidneys.
• Coronary arteries branch off the aorta and eventually deliver blood into capillaries in the heart muscle.
• Coronary arteries supply oxygenated blood to the muscle of the heart.
• Coronary heart disease is when the coronary arteries get blocked by layers of fatty material building up.