Alveoli and Gas Exchange in the Lungs

Structure of Alveoli

• Location: End of the bronchioles
• Shape: Resembles cauliflower; tiny air sacs
• Diagram Insight: Oxygen and carbon dioxide are supplied and removed through breathing

Gas Exchange Process

• Lining: One cell thick
  • Oxygen diffuses across the cell membrane lining the alveolus
  • Continues to diffuse across the blood capillary lining
  • Finally, diffuses into red blood cells and binds with hemoglobin to form oxyhemoglobin
  • Carbon dioxide follows the reverse path to exit the body
• Concentration Gradient: Maintained by constant supply and removal of gases through breathing and blood flow

Features of Gas Exchange Surface

1. Large Surface Area:

• Provided by shape and number of alveoli

2. Thinness:

• Only one cell thick, short diffusion pathway

3. Moist Lining:

• Allows gases to dissolve and diffuse across the lining

4. Good Blood Supply:

• Dense network of blood capillaries around each alveolus

Microscopic View of Lung Tissue

• Capillary Network: Zigzag crisscross mesh
• Red Blood Cells: Visible as individual red splotches

Ventilation

• Good Air Supply:
  • Ensured through effective breathing

Exam Tips

• **Features for Efficient Gas Exchange: **
  • Large surface area from numerous alveoli
  • One cell thick surface for short diffusion pathway
  • Dense capillary network supplying blood