gas exchange

• Suggest and explain how a reduced tidal volume affects the exchange of carbon dioxide between the blood and the alveoli.

  • Less carbon dioxide exhaled
  • (So) reduced concentration gradient (between blood and alveoli)
  • Less/slower movement of carbon dioxide out of blood
• • In fish, blood leaving (V) has more oxygen than water leaving (E) than in humans
  • the difference in V and E is greater in fish than in humans

  
• Explain how the counter-current principle allows efficient oxygen uptake in the fish gas exchange system.

  • Blood and water flow in opposite directions
  • concentration gradient maintained along length of lamella
• Haematoxylin solution stains DNA a blue colour and Iodine solution stains starch a blue-black colour.

  The scientist used haematoxylin solution and not iodine solution to stain the lung tissue. Suggest why.

  • This lung tissue does not contain starch;
  • Nucleus within lung tissue cells contains DNA
• • risk with asthma and living with cat or dog is statistically significant
  • risk with obesity is highly significant
  • risk with asthma and burned wood indoors is not statistically significant

  
• If alveolar epithelium cells die inside the human body they are replaced by non-specialised, thickened tissue.

  Explain why death of alveolar epithelium cells reduces gas exchange in human lungs.

  • Reduced surface area
  • Increased distance for diffusion
  • Reduced rate of gas exchange