These days it’s difficult to go watch a movie without having to sit through short videos that tell you it’s bad to smoke. By now you probably know that smoking is bad for your lungs, but do you know why?

What happens when you smoke?

Your respiratory system has a highly efficient housekeeping system. Sticky mucus present in the tubules trap dirt and germs, and tiny broomstick like cilia clear these foreign particles from the passageways.

Even as a smoker takes the first puff, he or she is inhaling thousands of chemicals into the lungs – many, cancer-causing.

Usually, such an invasion of particles would spring the housekeeping system into action, and these nasty particles would be swept away, in the process making us cough.

However, the nature of the chemicals inhaled during smoking is such that it paralyzes and kills the cilia. It renders them incapable of doing its job. As a result our airways are not cleaned up even though they are being dirtied.

Why do smokers cough?

As the cilia dies off, the mucus stops being swept off by it, so the person must cough the mucus out. This is what causes the smoker’s cough.

Smokers often wake up in the morning coughing, but when they light their first cigarette of the day, they begin killing the cilia again. The coughing subsequently ceases.

The smoker mistakes the lack of coughing as a good sign, and keeps smoking without realising that this is because their cilia is suffering.

How is breathing affected?

Since there is no cilia, mucus is now accumulating and clogging the passageways. Lungs get congested, and the disease-causing organisms trapped in the mucus come in contact with the smoker’s respiratory system. As a result, the smoker falls sick more often.

Accumulating mucus thickens the walls of the airways of the lungs, called bronchioles. This makes breathing difficult, and ruptures the air sacs. Burst air sacs worsen coughing.

A lot of the chemicals you inhale become tar and get stuck to your throat and lungs. This tar can kill healthy lung cells.

How can this cause lung cancer?

All these changes in the smoker’s respiratory system sometimes cause the bronchial cells to start dividing faster than usual. These dividing cells eventually displace the cells which have cilia. Many of these uncontrolled cells begin resembling cancer cells – large, misshapen, and having abnormal number of chromosomes. If this is allowed to keep happening, eventually a tumour could be formed.

nandita.j@thehindu.co.in