Lecture on the Respiratory System

Introduction

• Focus on the respiratory system, specifically on gas exchange within the lungs.
• Main functions:
  • Oxygen into the blood.
  • Offload CO2.
  • Control pH.
• Importance: Oxygen is needed for aerobic metabolism providing ATP; CO2 is a byproduct.

Maximizing Gas Exchange

1. Physical Principles:

   • Physics of Gases:
     • Model using a beaker: Air above water as a model for lungs.
     • Gas pressure from collisions of gas molecules.
     • Ideal Gas Law: Relationship between pressure, volume, temperature, and number of gas molecules.
     • Boyle's Law: Pressure and volume relationship (PV = constant).
     • Dalton's Law: Partial pressure concepts; influence of individual gas proportions on total pressure.

2. Blood Chemistry:

   • Solubility of gases in blood:
     • CO2 is more soluble than O2, creating challenges for oxygen transport.
     • Plasma improves O2 solubility compared to water.
     • Hemoglobin in red blood cells is crucial for O2 transport.

3. Oxygen Transport and Dissociation Curves:

   • Oxygen dissociation curve: Relationship between O2 saturation and partial pressure.
   • Curve affected by: pH, temperature, CO2 levels.
   • Exercise impacts curve: Lower pH, higher temperatures, increase in CO2 favor O2 release.

CO2 Transport

• Methods of CO2 transport:
  • Dissolved in plasma (7%).
  • Bound to hemoglobin (23%).
  • Converted to bicarbonate in red blood cells (70%).
  • Bicarbonate and proton formation lead to pH changes.
  • Exchange in lungs reverses bicarbonate formation.

Summary

• Gas exchange is driven by physical principles and blood chemistry.
• Hemoglobin is dominant in O2 transport.
• CO2 transport mainly through bicarbonate.
• Effective gas exchange ensures cells receive oxygen and offload CO2 efficiently.

Conclusion

• Respiratory system's role in maintaining efficient gas exchange.
• Comparison with other physiological systems (digestive, renal) will be discussed later.