Gas exchange

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  • Gas exchange
    • ventilation maintains concentration gradient of oxygen and carbon dioxide between air in alveoli and blood flowing in adjacent capillaries
      • happens by diffusion between air in the alveoli and blood flowing in adjaent capillaries
    • type I pneumocytes are extremely thin alveolar cells that are adapted to carry out gas exchange
    • type II pneumocytes secrete a solution containing surfactant that creates a moist surface inside the alveoli to prevent the sides of the alveolus adhering to each other by reducing surface tension
      • surfactant helps oxygen to diffuse to the blood
    • air is carried to the lungs in the trachea and then to the alveoli in bronchioles
      • trachea
        • lungs with bronchus
          • bronchioles
            • alveoli
    • muscle contraction cause the pressure change inside the thorax that force air in and out of the lungs to ventilate them
      • inspiration
        • diaphram downwards and flatterns
        • ribcage upwards and outwards
        • volume increases, pressure descreases
      • expiration
        • diaphram upwards and becomes more domed
        • ribcage moves downwards and inward
        • volume decrease, pressure increases
    • different muscles are required for inspiration and expiration because muscles only do work when they contract
      • antagonistic pairs


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