Question

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 (cm3)	Blood leaving lungs  (cm3)
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. 

Answer 1

1.   
   • Blood entering lungs has lower concentration of O₂ and higher concentration of CO₂ since most O₂ has been used up in respiration, yielding more CO₂
   • Blood leaving lungs has lower CO₂ levels 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.