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Bronchitis is the inflammation of the bronchi and is a commonly seen winter condition. The bronchi (the air passages leading into the lungs) are formed by the division of the trachea (the main windpipe leading from the larynx [Adam's apple] down through the neck into the chest). The trachea branches left and right into the bronchi which branch to supply lung lobe with the means for air to pass in and out.

Like the trachea, the bronchi are formed of cartilage rings overlain with muscle. One layer of muscle runs lengthwise along the tube; the other layer is circular. These muscles regulate the diameter of the air passages.

A common cold or extended exposure to cold temperatures or air pollution over time may lead to bronchitis (the suffix "-itis" means inflammation). A cough and sore throat are the primary symptoms but difficulty in breathing and development of a fever are also characteristics. This sudden and short-lived bronchitis is called acute bronchitis. This is easily cured with aspirin in more serious cases an antibiotic. Acute bronchitis usually causes no long-term problems.

Chronic bronchitis is a more serious condition. Chronic means it is a condition that persists over a long period of time. Chronic bronchitis is a disease of cigarette smokers and is often accompanied by emphysema. Emphysema is a condition in which lung tissue is destroyed and the capacity to breathe is seriously impaired.

The form of bronchitis associated with emphysema is called chronic obstructive pulmonary disease (COPD) and is difficult to cure. It is often difficult to tell whether the respiratory problems associated with COPD are the result of emphysema or chronic bronchitis. Some physicians consider the two conditions to be synonymous: if one has chronic bronchitis one also has emphysema.

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