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On the left, a schematic representation of the tracheobronchial tree as a dichotomous tubular tree structure (own figure). On the right, a schematic representation of the alveoli on the airway walls of an acinus (Picture by Patrick J. Lynch, medical illustrator/Wikimedia Commons. License: Creative Commons Attribution 2.5 License 2006. Bronchial anatomy detail of alveoli and lung circulation).
