Final answer:
The movement of substances through organs like the respiratory system is enabled by the rhythmic beating of cilia on the epithelial lining, forming a mucociliary escalator that helps clear trapped particles and pathogens.
Step-by-step explanation:
The movement of substances through hollow, tube-like organs such as the respiratory system is made possible by the beating of cilia on the epithelial lining of the organ. These ciliated epithelial cells have hair-like projections that beat rhythmically to move mucus or other substances through a duct. This movement is particularly significant in the respiratory system, where it forms a mucociliary escalator that sweeps particles of dust and pathogens trapped in the mucus toward the throat to be swallowed and destroyed by the stomach's acidic environment.