Fig. 4:  This Figure illustrates the epithelial mucosa, with the mucus-producing structures (glands on the left side, goblet cells in the middle of the chart), with the mucous bilayer, watery layer directly on the surface of the cells and the gel layer directly above.^[1]  The cilia move in the watery layer in a coordinated manner, moving slowly to the periphery of the lungs and quickly in the other direction, thereby touching the gel layer and transporting the mucous cephalad.