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The table below shows the volume of gases contained in 100cm3 of a blood sample tapped at two points in the mammalian circulatory system

Gas Blood entering lungs
Blood leaving lungs
 Oxygen 8.65 20.25
 Nitrogen 0.75 0.75
 Carbon (IV) oxide 55.60 31.65
  1. Account for the difference in the gaseous composition of
    • Blood entering the lungs; 
    • Blood leaving the lungs. 
  2. Name the blood vessel through which blood enters the lungs. 
  3.  Explain why most athletes prefer training from high altitude areas. 

1 Answer

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    • Blood entering lungs has lower concentration of O2 and higher concentration of COsince most Ohas been used up in respiration, yielding more CO2
    • Blood leaving lungs has lower COlevels and higher O2 levels since it has been purified. volume of nitrogen remains unchanged as it isn't used up during respiration.
  2. Pulmonary artery
  3. High altitude areas have low oxygen concentration, thus the body produces more red blood cells, increasing amount of oxygen carried around the body for respiration, making athletes more energetic.
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