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6.4 Gas Exchange (Mechanism of ventilation (:star: Airways for ventilation…

- - - - has rings of cartilage in wall of trachea and bronchus ; keep it open even when pressure inside lower than surrounding
      - bronchioles have smooth muscles fibres in walls, allowing width to vary
  - - - pressure conversely with volume of gases
      - e.g: movement of diaphragm and ribcage, external and internal intercostal muscles
- - - - fluid contains pulmonary surfactant ; molecules have structure similar to phospholipids in cell membranes
        
        hydrophilic heads facing water and hydrophobic tails facing air
        
        reduces surface tension and prevents water from causing alveoli to adhere (collpase of lung)