Gaseous Exchange Lecture Notes

Introduction

• Presented by Miss Angler
• Overview of gaseous exchange, including:
  • Movement from alveoli to blood
  • Transport of gases
  • Gaseous exchange at tissues

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Key Requirements for Successful Gaseous Exchange

1. Large Surface Area
   • Achieved by alveoli structure
2. Well Ventilated
   • Intercostal muscles and diaphragm facilitate movement of gases
3. Rich Blood Supply
   • Presence of capillary network around alveoli
4. Thin Membrane
   • Alveoli are one cell layer thick
5. Well Protected
   • Pleural membrane and ribs provide protection
6. Permanently Moist
   • Moisture is essential for gas diffusion

Gaseous Exchange at Alveoli

• Alveoli are balloon-like structures at the end of bronchioles
• Air does not reach alveoli directly, only diffuses down
• Tidal Air:
  • Air moves in and out of lungs, reaching halfway down bronchi
• Residual Volume:
  • Air remaining in lungs to prevent collapse; aids in easier inhalation

Mechanism of Gas Exchange

• Gases follow Partial Pressure gradients
• Oxygen: Higher concentration in alveoli compared to blood, diffuses into bloodstream
• Carbon Dioxide: Moves from blood into alveoli for exhalation

Process of Gas Diffusion

1. Oxygen Diffusion:
   • Enters moisture lining of alveoli
   • Diffuses across alveoli endothelium into capillaries
2. Carbon Dioxide Exchange:
   • Moves from red blood cells into alveoli, then exhaled

Transport of Gases in the Blood

• Oxygen Transport:
  • Binds to hemoglobin to form oxyhemoglobin
• Carbon Dioxide Transport:
  • Three primary methods:
    1. Forms bicarbonate ions with water
    2. Small amount binds to hemoglobin
    3. Dissolves in cytoplasm as carbonic acid

Exchange at Tissue Level

• Oxygen diffuses from blood to tissues
• Carbon dioxide diffuses from tissues to blood
• Gases move down concentration gradients
• Acidosis:
  • Slightly acidic conditions facilitate oxygen release from hemoglobin
  • Carbon dioxide increases acidity, promoting oxygen diffusion

Terminology Recap

• Alveoli: Site of gaseous exchange
• Tidal Air: Air flow in and out of lungs
• Residual Volume: Air remaining in lungs
• Diffusion: Movement from high concentration to low
• Erythrocytes: Red blood cells, transport oxygen and carbon dioxide
• Hemoglobin: Pigment that binds oxygen
• Bicarbonate Ions: Main form of carbon dioxide transport
• Carbonic Acid: Plays role in maintaining blood pH and facilitating gas exchange

Conclusion

• Importance of understanding gaseous exchange for exams
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