Lungs Health Article

Common diseases and disorders

Asthma is an intermittent disease characterized by a chronic inflammation of the airways, causing smooth muscle contraction in the airway. The causes vary from person to person and can include allergies, viral infections, environmental pollutants, mold, dust, dander, cigarette smoke, overexertion, and naturally released bronchiorestrictors. Ingested items such as food coloring, preservatives, and medications can trigger an attack.

Chronic obstructive pulmonary disease (COPD) refers to emphysema, chronic bronchitis, or a combination of the two. This category of disease is one of the major causes of death and disability in the world. These diseases restrict ventilation and the oxygenation of the blood.

Chronic bronchitis is characterized by excessive mucus production in the bronchi and chronic inflammatory changes in the small airways. The accumulation of mucus and thickening of inflamed airways obstruct the flow of air. It is primarily a result of cigarette smoking, although pollution may also play a role.

Emphysema is a major cause of hypoxia and is characterized by the destruction of the alveolar walls, and the atrophy and collapse of the lower airways. The lungs self-destruct through the secretion of proteolytic enzymes by white blood cells. Cigarette smoke stimulates the release of harmful enzymes and destroys the enzymes that normally protect against proteolysis. The proteolytic enzymes cause the breakdown of the alveolar walls. The damaged alveoli fuse and a gradual decrease in the surface area available for gas exchange results. Emphysema increases the work of breathing and, when severe enough, causes hypoventilation (inadequate venti lation). The obstruction caused by the collapse of the lower airways is accompanied with destruction of the lung's elastic tissues and the eventual collapse of the air ways.

Pneumonia is normally caused by bacterial or viral infection. It can be triggered by the inhalation of toxic chemicals, chest trauma, yeast, rickettsiae, and fungi. It is the inflammation and compaction of the lung parenchyma. The alveolar spaces fill with mucus, inflam matory cells, and fibrin.

Tuberculosis is caused by the infection of Mycobacterium tuberculosis. It can affect most organs but is most commonly found in the lungs. The bacteria cause lesions to be formed on the lungs and spread to other tissues. Pulmonary tissue in motion will be chroni cally affected and may eventually be destroyed, if left untreated. The erosion of lung tissue into the blood ves sels can result in life-threatening hemorrhages.

Other less common diseases of the lung include Legionnaire's disease, cystic fibrosis, histoplasmosis, coccidiomycosis, and Mycobacterium avium complex.

KEY TERMS

Interstitial space—The spaces found within organs and tissues.

Metabolism—A series of chemical and physiological changes in the body that either build larger molecules out of smaller molecules (anabolism) or break down larger molecules into smaller ones (catabolism).

Parenchyma—The active portion of an organ that fulfills its function (as opposed to purely structural portions of the organ).

Proteolysis—The breaking down of proteins by cleaving or hydrolyzing peptide bonds (the bonds connecting amino acids within the protein).

BOOKS

Bullock, John, et. al. National Medical Series for Independent Study—Physiology. Third ed. Williams & Wilkins, 1995.

Vander, Arthur et. al. Human Physiology—the Mechanisms of Body Function. Eighth ed. McGraw-Hill, 2001.

ORGANIZATIONS

The American Lung Association. 1740 Broadway, New York, NY, 10019. 212-315-8700. <http://www.lungusa.org/>.

OTHER

Thompson, B.H., W.J. Lee, J.R. Galvin, and J. S. Wilson. "Lung Anatomy." Virtual Hospital. University of Iowa Health Care. <http://www.vh.org/Providers/Textbooks/LungAnatomy/LungAnatomy.html>.

Sally C. McFarlane-Parrott