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LU7: RESPIRATORY SYSTEM (Respiratory organ in various animals (7. Lungs of…

- - - - Phylum Chordata
        
        moist, thin gills
        
        Buccal and opercular cavities draw water across gills.
        
        movement jaw & operculum pump water rich in oxygen through mouth & across gills.
        
        counter current exchange system in gill increase DP..
      - Limitations:
        
        no work on land.
        
        gill filaments collapse in less buoyant air.
        
        large surface area of gills expose to dry air.
    - - Phylum Chordata
        
        larva fish and amhibians
        eg. Neotenic salamander
        
        thin gills
        
        feather-like gills
        
        skin - additional respiratory surface
      - limitations:
        
        must be in constant motion.
        
        tissue delicate & cannot be protected
        
        small body size.
  - - - Alveoli
        
        large surface area. (eg. Mammals have elaborate network of thin air sacs)
        
        moist and one cell thick wall with capillaries.
        
        Diffusion: from alveoli (high oxygen level) to blood (low oxygen level).