1. Ms. L's symptoms include shortness of breath, a chronic cough productive of thick mucus,
and a "chest cold" of 2 months' duration. She was advised to quit smoking, a major cause of
lung irritation. These symptoms were caused in part by the obstruction of groups of alveoli
by mucous plugs. Ms. L was told that the mucus is not moving normally out of her airways
because the toxins in cigarette smoke paralyze small cell extensions that beat to create an up-
ward current. These extensions are called