The respiratory system can be divided into two compartments--the upper and lower respiratory tracts. The upper respiratory tract consists of the nose, nasal cavity and sinuses, pharynx, larynx and trachea. Infectious processes that cause dysfunction of these areas are classified as upper respiratory tract infections. Lower respiratory diseases and infections include the disease processes which take place in the lung. The structures of the lung include the bronchi, bronchioles and alveoli. A lung infection can involve any or all of these structures as well as the supporting tissues around them.
Infection and Inflammation
Inflammation is a reaction by the immune system attempting to repair an area of the body that has become damaged. When an organism that is foreign to the body escapes protective physical and chemical barriers, it is attacked by the immune system. Inflammation creates four effects: redness, heat, swelling and pain. In lung tissue, inflammation creates symptoms of difficult or painful breathing, cough and congestion.
Pneumonia
The most common lung infection is pneumonia. Pneumonia, according to the Mayo Clinic Online Library, is lung inflammation, most commonly caused by an infection. Pneumonia can develop from pathogenic viral, bacterial or fungal organisms. The book "Human Diseases: A Systemic Approach," by Mark Zelman lists the three different types of pneumonia as bronchopneumonia, lobar pneumonia and interstitial pneumonia, also known as "walking pneumonia." Symptoms of pneumonia include shortness of breath, chest pain, fever and a mucus-expelling cough. Pneumonia can be very serious, and if not well managed, it can lead to severe medical complications and even death.
Tuberculosis
Tuberculosis is the lung infection caused by the bacteria Mycobacterium tuberculosis. It is an infection that is very common worldwide, and a leading cause of death in many places. Tuberculosis spreads via respiratory droplets emitted by by coughing. Tuberculosis can turn into a systemic disease, if the respiratory infection is not properly controlled, notes Zelman. Bacterial invasion of the respiratory tissue will invoke an inflammatory response that will encapsulate and ward off the infection from the surrounding tissue. The affected lung tissue will die and the area will become calcified, appearing as a hardened structure on an X-ray. Screening tests for tuberculosis are very useful, and the antibiotics that treat the infection are highly effective.
Bronchitis
Bronchitis is an inflammation of the large and small bronchi that leads to increased mucus production and airway obstruction. Bronchitis can be acute or chronic, and acute forms are often brought on by infection. Viral infections are the most common cause of acute bronchitis, notes a 2002 American Family Physician journal article. Chronic bronchitis is defined by Zelman as three episodes of acute bronchitis that have lasted at least three months each and have occurred in the last two years. Bronchitis that has become chronic is usually attributable to chemicals, allergens or cigarette smoke. These irritants make the airways more reactive and more inclined to inflammation and mucus production.
Influenza
The flu is caused by a virus. It is generally associated with many upper respiratory symptoms and systemic indicators, like body aches and fatigue. However, influenza also leads to coughing, which indicates some lower respiratory involvement. it also can lead to pneumonia. Zelman explains that an influenza-induced pneumonia was responsible for killing the majority of the estimated 20 million people who died in the 1918-1919 flu epidemic.
References
- Mayo Clinic: Pneumonia -- Definition
- "Human Diseases: A Systemic Approach"; Zelman; 2010
- American Family Physician: "Diagnosis and Management of Acute Bronchitis"
