circulatory system

• substances transported by the blood:

  digested food - transported by blood plasma

  oxygen - from lungs to body by red blood cells

  carbon dioxide - produced in respiration, transported to lungs where breathed out

  hormones - transported in plasma

  waste - transported to kidneys for excretion
• Blood:

  • plasma - yellow liquid part of blood, transports soluble substances
  • red blood cells - transports oxygen red pigment hemoglobin
  • white blood cells - fight diseases as part of immune system
  • platelets - help blood clots
• red blood cells:

  • absorb oxygen from lungs and transport it through narrow blood vessels
  • biconcave disc, increases surface area for maximum absorption of oxygen
  • no nucleus, contain more hemoglobin
  • red pigment hemoglobin, the protein combines with oxygen
  • small and flexible so can fit through narrow blood vessels
  • thinner in center more light passes through

  
• white blood cells: ingest and destroy pathogens

  phagocyte - engulfs bacteria

  lymphocytes - produce antibodies

  1. engulfs bacterial cell
  2. cell is broken down by enzyme inside phagocyte
  3. process of ingesting pathogen called phagocytosis

  • they can change shape and also move (ingest bacteria and squeeze through capillary walls)

  
• Platelets: tiny cell fragments, wound must close and prevent blood loss and pathogen entry scabs do that

  • release chemicals that cause soluble proteins to form mesh of insoluble fibres across wound
  • stick together to form clumps that get stuck in the mesh
  • This develops into a scab, which protects the wound as it heals.
  • Red blood cells also get stuck in the mesh, forming a clot
• Arteries:

  • thick elastic muscular walls
  • blood under high pressure
  • internal lumen, blood passageway
  • carries oxygenated blood away from the heart
• Capillaries:

  • near every living cell and organ in body
  • walls one cell thick (easier diffusion)
  • very low pressure (more time for materials to be exchanged)
  • blood from arteries to veins
  • lumen very small
  • gases such as oxygen and carbon dioxide are exchanged here

  
• Vein:

  • carries deoxygenated blood to the heart
  • thin, less muscular walls
  • larger lumen increases rate of blood flow
  • blood under low pressure.
  • valves to prevent backflow of blood

  
• structure of blood vessels:

  
• Treating cardiovascular disease:

  • Statins - medication that controls blood cholesterol levels, may cause side effects
  • angioplasty - surgery to insert a small balloon into a blood vessel which is then inflated to remove a blockage, sometimes only temporary and risks
  • lifestyle changes - diet, exercise, stop smoking, reduces risk of heart disease and blood pressure, high level of willpower required to maintain changes
• what can increase risk of CVD?

  1. smoking - limits oxygen absorption so heart needs to work harder
  2. high blood cholesterol - plaque on artery walls
  3. diabetes
  4. overweight or obesity - fat around heart so needs to work harder
  5. lack of exercise - helps avoid obesity
  6. family history of heart disease - genetics
  7. ethnic background - south Asian statistically higher risk
  8. high blood pressure - strain on heart and blood vessels
• atherosclerosis: begins with damage to endothelial lining

  1. fatty cholesterol develops over time
  2. hard outer layer of plaque can crack
  3. platelets form blood clots around the cracks
  4. artery narrows even more
  5. blood flow blocked
  6. oxygen doesn't reach heart muscle so it dies

  
• angina and myocardial infraction:

  • the coronary arteries can be found surrounding the heart on the surface
  • CVD is caused by build up of fatty deposits, reduced blood flow to the heart, needs to work harder
  • life threatening as starving heart of blood, oxygen and nutrients
  • cause pains in chest known as angina
  • if blockage happens in brain can cause a stroke

  
• • pulmonary circulation - blood leaves the heart and travels to the lungs
  • systemic circulation - blood leaves the heart and travels to the body organs
  • called double circulation as blood passes through the heart twice
  • left side receives oxygenated blood from the lungs and pumps it to the body
  • right side receives de-oxygenated blood from the body and pumps it back to lungs
  • blood leaves through aorta

  
• The heart:

  • muscular organ
  • function is to pump blood
  • cardiac muscle of the heart contracts to pump blood from atria into ventricles and from ventricles into arteries
  • cardiac muscle of heart requires energy from respiration to continue to contract
  • supplied with glucose and oxygen required by coronary arteries

  
• • left ventricle thicker wall as has to pump blood all around the body
  • right ventricle only has to pump to the lungs which is close to the heart
  • for blood to be able to leave the heart it needs to be beating/contracting

  
• • oxygenated blood flows into the left atrium via the pulmonary vein from the lungs
  • left atrium contracts forcing the bicuspid valve open so that blood goes into the left ventricle
  • left ventricle contracts, which forced the bicuspid valve shut but opens the semilunar valve
  • blood flows out of the heart via the aorta