Gas Exchange System

Functions of the Gas Exchange System

• Maintain concentration or pressure gradient between air in alveoli and blood in capillaries.
  • Oxygen must diffuse from air into blood.
  • Carbon dioxide must diffuse from blood into air.

Importance of Gas Exchange

• Oxygen diffusion
  • Blood must be oxygenated for cells to receive oxygen for respiration.
  • Lack of oxygen leads to cell death.
• Carbon Dioxide removal
  • Blood must have low CO2 levels to prevent acidity.
  • CO2 makes blood acidic by forming carbonic acid, which splits into hydrogen ions and hydrogen carbonate ions, lowering blood pH.

Maintaining Concentration Gradient

• Oxygen:
  • High partial pressure/concentration in alveoli.
  • Low partial pressure/concentration in blood.
  • Oxygen diffuses down the gradient into blood.
• Carbon Dioxide:
  • High partial pressure/concentration in blood.
  • Low partial pressure/concentration in alveoli.
  • CO2 diffuses from blood into alveoli.

Re-establishing the Gradient

• For Oxygen:
  • Increase oxygen in alveoli by breathing in.
  • Heart contraction pushes deoxygenated blood to alveoli.
• For Carbon Dioxide:
  • Breathe out air to decrease CO2 in alveoli.
  • Heart contraction brings deoxygenated blood to capillaries.

Exam Tips

• Maintain concentration gradient by:
  • Lung ventilation: Ensures high oxygen and low CO2 in alveoli.
  • Heart contraction: Pushes deoxygenated blood to lungs, maintaining low oxygen and high CO2 in blood.

Key Terms

• Partial Pressure and Concentration: Can be used interchangeably when discussing gases.