circulatory system

• components and functions of blood

  • red blood cells
  • white blood cells
  • plasma
  • platelets
• function of red blood cells

  
  

  • carry oxygen molecules from the lungs to all cells in the body
  • biconcave discs to maximise surface area for oxygen to be absorbed
  • flexible so can fit through narrow blood vessels
  • no nucleus to create space for haemoglobin
• function of plasma

  • the liquid which carries components in the blood eg cells, platelets, amino acids, hormones
  • important for transport of carbon dioxide, digested food, urea, hormones
• function of white blood cells

  • wbc are part of the immune system (the body's defence against pathogens)
  • first type is phagocytes, where the pathogen is engulfed then killed
  • lymphocytes (which produce antibodies), where each pathogen has an antigen on their surface which a specific complementary antibody can bind to
  • once antibodies start to bind the pathogen, the pathogens clump together resulting in it being easier for wbc to find them
• function of platelets

  • platelets are fragments of cells that are involved in blood clotting + forming scabs where skin is cut
  • when skin is broken, platelets stop the bleeding and reactions occur within blood plasma
  • platelets release chemicals that cause soluble fibrinogen proteins to convert into insoluble fibrin and form an insoluble mesh across the wound, trapping rbc and forming a clot which eventually dries and develops into a scab to protect the wound from bacteria entering

  
• importance of blood clotting

  • prevents continued/significant blood loss from wounds
  • scab formation seals the wound with an insoluble patch that prevents entry of microorganisms causing infenction
  • it remains in place until new skin has grown underneath it, sealing skin again
• 3 main types of blood vessels

  • vein
  • artery
  • capillary
• key features of arteries

  • carry oxygenated blood (except pulmonary artery) at high pressure away from the heart
  • *thick muscular walls containing elastic fibres to withstand high pressure of blood + maintain the blood pressure as it recoils after the blood passes through
  • *narrow lumen to also maintain high pressure
  • blood flows through at a fast speed
• key features of veins

  • carry deoxygenated blood at low pressure towards heart (except pulmonary artery)
  • * large lumen which reduces resistance to blood flow under low pressure
  • valves prevent backflow of blood bc it's under low pressure
  • blood flows through at a slow speed
• key features of capillaries

  • carry blood at low pressure within tissues
  • carry oxygenated + deoxygenated blood
  • * walls are once cell thick (short diffusion distance) so substances can easily diffuse in/out of them
  • * leaky walls allow blood plasma to leak out and form tissue fluid surrounding cells
  • speed of blood flow is slow
• What is the condition characterized by the buildup of fatty material in coronary arteries?

  Coronary heart disease
• What is primarily formed from the buildup of plaque in coronary arteries?

  Cholesterol
• What happens to a coronary artery when it becomes partially or completely blocked by plaque?

  It loses elasticity and cannot stretch to accommodate blood flow
• What is the consequence of reduced blood flow through arteries due to blockage?

  There is a lack of oxygen for the heart
• What condition results from partial blockage of coronary arteries?

  Angina (chest pains)
• What occurs when there is a complete blockage of coronary arteries?

  Cells in that area of the heart cannot respire aerobically, leading to a heart attack
• What are the effects of coronary heart disease on the heart?

  • if a coronary artery becomes partially/completely blocked by plaque, it loses elasticity + can't stretch to accommodate the blood being forced through when the heart contracts
• treatment of coronary heart disease

  • using a stent to increase the width of the lumen
  • prescribing statins to lower blood cholesterol
• risk factors of coronary heart disease

  • obesity: carrying extra weight puts a strain on the heart, can also lead to type 2 diabetes which further damages blood vessels
  • high blood pressure: increases force of blood against artery walls, leads o vessel damage
  • high cholesterol: speeds up buildup of plaque in arteries leading to blockages
  • smoking: chemicals in smoke incrs plaque build up and blood pressure, carbon monoxide reduces oxygen carrying capability of rbc