Development of the lung of the brushtail possum, Trichosurus vulpecula.

The developing lung of the brushtail possum, Trichosurus vulpecula, was studied by light microscopy, and transmission electron microscopy was used to study the morphology of the conducting airways in the adult. Bronchi did not extend beyond the hilus of each of the six lobes of the lung, and lobules were supplied by major bronchioles. By 105 days post partum, bronchi and bronchioles were fully formed, coinciding with the emergence of mucosal associated lymphoid tissue (MALT), which preceded alveolar maturation by approximately 20 days. In the adult lung, goblet cells were rarely observed in the mucosal epithelium of bronchi, whereas Clara cells were present in the mucosa of all airways, increasing proportionately as the conducting and respiratory portions narrowed distally. Although the airways of the possum lung have a poorly developed mucociliary blanket, this may be compensated for by the large numbers of Clara cells and adequate supply of MALT.