One major type of respiratory disease is emphysema. The major cause of this condition occurs when Fred inhales the smoke from a cigarette, thousands of chemicals in the smoke irritate his bronchial tubes and lungs. Once the cilia can no longer push foriegn matter out of Fred's lungs, the thousands of chemicals can now penetrate deeper into his lungs and cause futher damage. Emphysema is characterized in a smoker's difficulty in breathing. The smoker' s lungs lose their ability to suck in or force out sufficient amounts of air, and as times goes on lung tissue is actually destroyed.
Cigarette smoking is also a major cause of cancer.
The chemicals in the cigarette's smoke alter the DNA of a normal cell in the lungs. When the altered cell divides and produces a new cell, called a daughter cell, the new cell carries the DNA from its parent cell that has been altered. The cancer cells will then start to duplicate and exhaust the nutrients of the healthy tissues in the lungs, causing them to die.