motile cilium

"In effect, the [motile cilium] is a nanomachine composed of perhaps over 600 proteins in molecular complexes, many of which also function independently as nanomachines."

Subjective lung irritation not based upon the amount of matter crossing the semipermeable gas exchange surfaces deep in the lungs, rather the primary factor is amount of matter which adheres to motile cilium.

The axoneme of primary cilia typically has a ring of nine outer microtubule doublets (called a 9+0 axoneme), and the axoneme of a motile cilium has two central microtubule doublets in addition to the nine outer doublets (called a 9+2 axoneme).