Fig. 1.

Alcian blue-stained bundles from piglet submucosal glands are transported cephalically. A. Pig trachea. B. Distal trachea and primary bronchi mounted in the experimental chamber. C. Dorsal side of piglet trachea with bifurcation and charcoal collected in the mucus. Mucus was moved cephalically and outwards as indicated by the green arrows. D. The ventral side of the trachea with Alcian blue-stained bundles moving according to the arrows, up and ventrally. E. Pig trachea mounted as in B with Alcian blue-stained bundles moving upwards over the surface in Movie S1. Images at 0, 6, 12 and 18 s from the same surface of a time-lapse recording at 16 times the original speed. Red arrows point to the same mucus bundles. F. Diameter of Alcian blue-stained bundles in airways, mean of 8 bundles from 3 pigs. G. SEM image of a pig trachea with bundles coming out of submucosal glands. H. Mucus bundle and cilia appear to interact.