Sticky mucus in the lungs traps pathogens. The mucus is normally swept out of the lungs by the cilia on the epithelial cells lining the trachea, bronchi and bronchioles. If this does not happen, bronchitis can occur. In addition, cigarette smoke contains harmful chemicals that damage the epithelial cells, leading to a build-up of mucus and a smoker's cough. Smoke also irritates the bronchi, causing bronchitis.
The liver removes alcohol from the bloodstream. It has enzymes that break down alcohol but the products of the reactions involved are toxic. They damage the liver and over time this can lead to cirrhosis. This means that the liver cannot function properly anymore.
Diabetes is a disorder in which the blood glucose levels remain too high. Type 2 diabetes is caused by a person's cells becoming resistant to insulin so glucose is not removed from the blood.
This disease can be controlled by improving a person's diet. Levels of sugar and fat in the diet need to be reduced. Taking regular exercise helps to control the disease as the glucose is used up in respiration, therefore lowering blood glucose levels. There is a link between rising levels of obesity and increasing levels of Type 2 diabetes. As obesity is a risk factor for Type 2 diabetes, doctors are keen to monitor the situation.