Cilia are tiny hair-like organelles that reside on the surface of cells. In the human body, many are found on cells where they sweep debris away from the lungs and nasal cavities. They also line the Eustachian tubes and sinuses, as well as the fallopian tubes in women. For each ciliated cell in the body, there are between 100 and 200 cilia, each one anchored by another organelle known as the basal body. Constructed of hollow cylindrical microtubules, each basal body is arranged in the same orientation to allow the movement of fluid and particles to occur in one direction.
There are two types of cilia: motile and non-motile. The former continuously move in a wave-like fashion in a single direction, while the latter function as sensory organs that respond to stimulus. All cilium, however, are composed of several types of proteins that work synergistically together to stimulate ciliary motion. If one protein is absent or becomes damaged, then the organelles may remain rigid. Polycystic kidney disease and tubal pregnancies, for example, are due to those that do not function correctly.
The most common reason to suffer damaged or paralyzed cilia, however, is smoking. Normally, healthy ones in the bronchial tubes work in sync with specialized cells that produce mucous to capture and remove impurities from the lungs. Smokers, on the other hand, are subjected to about 4,000 toxic chemicals in cigarette smoke, including arsenic, methane, and carbon monoxide. This damages the organelles, and dirt, environmental pollutants, and toxins from cigarette smoke remain in the lungs. Furthermore, these toxins migrate from the lungs via the bloodstream to other organs.
In response to the presence of excess irritants, mucous cells in the lungs become stimulated to produce more mucous than they normally would. Of course, with damaged cilia, the lungs have no means of moving the mucous out. This usually results in an unproductive cough. In fact, the damage caused by smoking leaves the smoker at significantly higher risk for frequent respiratory infections, or chronic bronchitis.
Continued smoking may eventually lead to chronic obstructive pulmonary disease (COPD, including chronic bronchitis and emphysema) or lung cancer. In fact, smoking eventually destroys the cilia, which may then be displaced by an excessive number of basal cells or squamous cells. Over time, these cells may become cancerous. They may also become rogue, escaping through lung tissue and invading other parts of the body.
Remarkably though, stopping smoking can undo the damage to cilia rather quickly. In fact, they begin to repair themselves and regenerate in number within only three days after quitting. It should be noted that coughing is a common side effect to this process and may last from a few days to several weeks. This is because the restored cilia are working overtime to remove impurities and mucous from the lungs. If cough persists for more than eight weeks, however, a medical professional should be consulted.