Fig. 6
Modified from [34]
Physical disector for counting of alveolar openings to estimate alveolar number. Counting event is the presence of an alveolar opening in one section (left, indicated by arrowheads at the free septal edges that belong to the entrance ring) but not the other (right) where the alveolus is closed by a bridge (arrow). The disector volume is defined by the area of the unbiased counting frame [11] multiplied with the distance between the two sections (here 9 µm). The unbiased counting frame has inclusion lines (green) and exclusion lines with extensions (red). The counting rule allows disector counts of particles inside the counting frame, where they may touch the inclusion line, but not the exclusion line.