Lung diseases are some of the most
common medical conditions worldwide. Tens of millions of people suffer from
lung disease in the U.S. Smoking,
infections, and genetics are responsible for most lung diseases.
The lungs are part of a complex
apparatus, expanding and relaxing thousands of times daily to bring in oxygen
and expel carbon dioxide. Lung disease can result from problems in any part of
this system.
Lung
Diseases Affecting the Airways
The trachea (windpipe) branches into
tubes called bronchi, which in turn branch to become progressively smaller
tubes throughout the lungs. Diseases that affect the airways include:
Asthma: The
airways are persistently inflamed, and may occasionally spasm, causing
wheezing and shortness of breath. Allergies,
infections, or pollution can trigger asthma's symptoms.
Chronic obstructive pulmonary disease (COPD): Lung conditions defined by
an inability to exhale normally, which causes difficulty breathing.
Chronic bronchitis:
A form of COPD characterized by a chronic productive cough.
Emphysema:
Lung damage allows air to be trapped in the lungs in this form of COPD.
Difficulty blowing air out is its hallmark.
Acute bronchitis: A sudden infection of the airways,
usually by a virus.
Cystic fibrosis: A genetic condition causing poor clearance of mucus
from the bronchi. The accumulated mucus results in repeated lung
infections.
Lung
Diseases Affecting the Air Sacs (Alveoli)
The airways eventually branch into
tiny tubes (bronchioles) that dead-end into clusters of air sacs called
alveoli. These air sacs make up most of the lung tissue. Lung diseases
affecting the alveoli include:
Pneumonia:
An infection of the alveoli, usually by bacteria.
Tuberculosis: A slowly progressive pneumonia caused by the bacteria
Mycobacterium tuberculosis.
Emphysema results from damage to the fragile
connections between alveoli. Smoking is the usual cause. (Emphysema also
limits airflow, affecting the airways as well.)
Pulmonary edema: Fluid leaks out of
the small blood vessels of the lung into the air sacs and the surrounding
area. One form is caused by heart failure and back pressure in the lungs' blood
vessels; in another form, direct injury to the lung causes the leak of
fluid.
Lung cancer has many forms, and may develop in any part of the
lungs. Most often this is in the main part of the lung, in or near the air
sacs. The type, location, and spread of lung cancer
determines the treatment options.
Acute respiratory distress syndrome (ARDS):
Severe, sudden injury to the lungs caused by a serious illness. Life
support with mechanical ventilation is usually needed to survive until the
lungs recover.
Pneumoconiosis: A category of conditions caused by the
inhalation of a substance that injures the lungs. Examples include black
lung disease from inhaled coal dust and asbestosis from inhaled asbestos
dust.
Lung
Diseases Affecting the Interstitium
The interstitium is the
microscopically thin, delicate lining between the lungs' air sacs (alveoli).
Tiny blood vessels run through the interstitium and allow gas exchange between
the alveoli and the blood. Various lung diseases affect the interstitium:
