respiratory system 2

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  • Created by: P15198914
  • Created on: 15-02-16 19:16
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  • the respiratory system
    • the bronchi, bronchioles and alveoli
      • the trachea divides primary right and left bronchi which enter the lungs
      • the bronchi keep dividing into smaller bronchi- finally giving rise to the bronchioles
      • the bronchioles divide into alveolar ducts which end in alveoli
      • the bronchi and bronchioles form the respiratory tree
    • the alveoli
      • the site of gas exchange with blood
      • provide a large surface area
      • each is closely associated with a capillary bed coming from the pulmonary artery
      • the wall of the alveolus+ the wall of the capillary= the respiratory membrane
      • gas exchange occurs by diffusion across the respiratory membrane as the blood flows past
      • the alveolar epithelium contains 2 cell types
        • alveolar type 1 cells- allow diffusion of gases
        • alveolar type 2 cells- secrete surfactant
    • inspiration
      • pressure in the lungs must be lower than atmospheric pressure
      • diaphragm contracts, intercostals  contract- rib cage moves up and expands
        • lung volume increases
          • pressure in the lungs drops below atmospheric pressure
            • air flows in
    • expiration
      • pressure in the lungs must be above atmospheric pressure
      • diaphragm relaxes, intercostals relax- elastic recoil of ribs and the ribs drop
        • lung volume decreases
          • pressure in the lungs exceeds atmospheric pressure
            • air flows out


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