Basic avian pulmonary design and flow-through ventilation in non-avian theropod dinosaurs

@article{OConnor2005BasicAP,
  title={Basic avian pulmonary design and flow-through ventilation in non-avian theropod dinosaurs},
  author={Patrick M. O’Connor and Leon P. A. M. Claessens},
  journal={Nature},
  year={2005},
  volume={436},
  pages={253-256}
}
Birds are unique among living vertebrates in possessing pneumaticity of the postcranial skeleton, with invasion of bone by the pulmonary air-sac system. The avian respiratory system includes high-compliance air sacs that ventilate a dorsally fixed, non-expanding parabronchial lung. Caudally positioned abdominal and thoracic air sacs are critical components of the avian aspiration pump, facilitating flow-through ventilation of the lung and near-constant airflow during both inspiration and… 
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TLDR
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