Pores of Kohn are channels running between two adjacent alveoli across the alveolar wall within a lobule of the lung. They are distinct from the connections alveoli make with each other by their common opening onto one alveolar sac or alveolar duct; in these cases, the alveolar wall is not breached. 10-14 micrometres in diameter, the pores are encircled by irregularly-spaced elastic and reticular fibres.
The pores may be an adaptation to permit gaseous transit to alveoli that have been blocked by proximal obstruction. However, this collateral route may be disadvantageous in that it provides a path for the dissemination of infection of malignancy.