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Exchange of Gases

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Estimated time: 4 minutes
  • Exchange of Gases - in Humans
CBSE: Class 12

Key Points: Exchange of Gases

  • Gas exchange occurs between alveoli, blood, and tissues by simple diffusion based on pressure and concentration gradients.
  • Partial pressure is the pressure exerted by an individual gas in a mixture, represented as pO₂ for oxygen and pCO₂ for carbon dioxide.
  • O₂ moves from alveoli (pO₂ = 104) → blood → tissues (pO₂ = 40); CO₂ moves in the opposite direction - from tissues (pCO₂ = 45) → blood → alveoli (pCO₂ = 40).
  • CO₂ is 20-25 times more soluble than O₂, so it diffuses much more easily through the diffusion membrane.
  • The diffusion membrane has 3 layers: thin squamous epithelium of alveoli, endothelium of alveolar capillaries, and the basement membrane between them. Total thickness is less than 1 mm.
  • Alveoli are the primary sites of gas exchange. Solubility of gases and the thickness of membranes also affect the rate of diffusion.
  • Negative intrapleural pressure (pressure in the pleural cavity, lower than atmospheric pressure) is the key factor that prevents collapse of the lungs.

Shaalaa.com | Breathing and Exchange of Gases part 11 (Exchange of gases, Mechanism)

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