Gas Exchange System and Maintaining Concentration Gradient

Importance of Gas Exchange

• Gas Exchange Function: Maintains a concentration or pressure gradient between air in the alveoli and blood in the capillaries.
• Oxygen Diffusion: Oxygen must diffuse from the air into the blood to keep cells oxygenated for respiration.
  • Lack of oxygen leads to cell death.
• Carbon Dioxide Removal: Carbon dioxide must diffuse from the blood into the air to prevent blood acidity.
  • High CO2 levels form carbonic acid, lowering blood pH and making it acidic.

Concentration Gradient

• Definition: A concentration or pressure gradient exists when there is a difference in concentration or pressure of gases across two areas.
• Oxygen Gradient:
  • High partial pressure of oxygen in alveoli.
  • Low partial pressure of oxygen in the blood.
  • Positive gradient for oxygen diffusion from alveoli to blood.
• Reestablishing Gradient:
  • When oxygen levels equalize, diffusion stops.
  • Increase oxygen concentration in alveoli by breathing in.
  • Introduce deoxygenated blood by heart contraction.

Role of Breathing and Heart Contraction

• Breathing (Ventilation):
  • Inhaling introduces more oxygen into alveoli.
  • Exhaling removes carbon dioxide from alveoli.
• Heart Contraction:
  • Pushes deoxygenated blood to the lungs.
  • Maintains low oxygen and high carbon dioxide in blood, maintaining the gradient.

Comparing Oxygen and Carbon Dioxide

• Oxygen:
  • Diffuses from higher concentration in alveoli to lower concentration in blood.
• Carbon Dioxide:
  • Diffuses from higher concentration in blood to lower concentration in alveoli.

Maintaining the Gradient

• Lung Ventilation: Ensures alveoli have high oxygen and low carbon dioxide concentrations.
• Heart Activity: Ensures blood near alveoli has low oxygen and high carbon dioxide concentrations.
• Partial Pressure vs. Concentration: Terms can be used interchangeably for gases in this context.

Summary

• For effective gas exchange, the body must maintain a concentration gradient between alveoli and blood.
• Achieved through regular breathing and heart contractions to ensure continuous diffusion.
• For exams, mention lung ventilation and heart contractions as key factors in maintaining the concentration gradient.