Pulmonary Alveolus - Diseases

Diseases

• Acute respiratory distress syndrome (ARDS) is a severe inflammatory disease of the lung. Usually triggered by other pulmonary pathology, the uncontrolled inflammation leads to impaired gas exchange, alveolar flooding and/or collapse, and systemic inflammatory response syndrome. It usually requires mechanical ventilation in an intensive care unit setting.

• Infant respiratory distress syndrome (IRDS) is a syndrome caused by lack of surfactant in the lungs of premature infants.

• In asthma, the bronchioles, or the "bottle-necks" into the sac are restricted, causing the amount of air flow into the lungs to be greatly reduced. It can be triggered by irritants in the air, photochemical smog for example, as well as substances that a person is allergic to.

• Emphysema is another disease of the lungs, whereby the elastin in the walls of the alveoli is broken down by an imbalance between the production of neutrophil elastase (elevated by cigarette smoke) and alpha-1-antitrypsin (the activity varies due to genetics or reaction of a critical methionine residue with toxins including cigarette smoke). The resulting loss of elasticity in the lungs leads to prolonged times for exhalation, which occurs through passive recoil of the expanded lung. This leads to a smaller volume of gas exchanged per breath.

• Chronic bronchitis occurs when an abundance of mucus is produced by the lungs. The production of this substance occurs naturally when the lung tissue is exposed to irritants. In chronic bronchitis, the air passages into the alveoli, the broncholiotes, become clogged with mucus. This causes increased coughing in order to remove the mucus, and is often a result of extended periods of exposure to cigarette smoke.

• Cystic fibrosis is a genetic condition. A mutation of the cystic fibrosis transmembrane conductance regulator gene causes defective CFTR proteins, which are transmembrane proteins that function in Cl- transport in wet epithelia. Because wet epithelium is such a ubiquitous and multipurpose tissue type, CF has myriad deleterious effects, some of the most serious of which are severe respiratory problems. Many of the mechanisms by which CF causes damage or inadequate function in the wet epithelia of other tissues, such as the digestive and reproductive tracts, are well-understood. CF's mechanisms in causing lung disease, however, remain poorly elucidated. One popular hypothesis suggests increased viscosity due to increased salinity of the mucous secreted by glands of the pseudostratified respiratory epithelium, causing difficulty in maintaining normal respiratory tract mucociliary clearance. The frequency of certain specific bacterial infections (Pseudomonas, H. flu, Staph) has prompted two other popular categories of hypotheses: that the high salt content may interfere with defensins and lysosome, and/or may encourage the growth of the several bacterial species typically infecting the ordinarily-sterile lower lungs of CF patients. Regular treatment is usually required—primarily percussive therapy and antibiotics. Promising research into gene therapies is taking place.

• Diffuse interstitial fibrosis

• Lung cancer is a common form of cancer causing the uncontrolled growth of cells in the lung tissue. Due to the sensitivity of lung tissue, such malignant growth is often hard to treat effectively.

• Pneumonia is an infection of the lung parenchyma, which can be caused by both viruses and bacteria. Cytokines and fluids are released into the alveolar cavity and/or interstitium in response to infection, causing the effective surface area of gas exchange in the lungs to be reduced. If this happens to such a degree that the patient cannot draw enough oxygen from his or her environment to maintain cellular respiration, then the victim may need supplemental oxygen.

• Cavitary pneumonia is a process in which the alveoli are destroyed and produce a cavity. As the alveoli are destroyed, the surface area for gas exchange to occur becomes reduced. Further changes in blood flow can lead to decline in lung function.

• Pulmonary contusion is a bruise of the lung tissue.