Lungs - Anatomy, Functions, Problems and Diseases
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The Lungs

Authored by Venkat Gunnam on 20 Mar 2013 - 18:33

The lungs are the organs of respiration found in mammals and other developed organisms. They are found in the chest cavity, adjacent to the spine, one on either side of the heart. The trachea (windpipe) divides into two large bronchi that enter the lungs. These bronchi undergo multiple divisions within the lungs, and terminally form bronchioles. Subsequent divisions of bronchioles give rise to alveolar sacs, which resemble bunches of grapes, with the grapes themselves called alveoli. These alveoli are highly vascularised, and it is here that air exchange occurs. Deoxygenated blood is pumped to the lungs and exchanged with oxygen, and re-enter systemic circulation.

          Credit: Dr. Ram Prasad

The left and right lungs are not identical. The right side consists of three lobes, while the left has two, and a special indentation called the cardiac notch visible, which is there to accommodate the heart. The lobes of the lungs are in turn surrounded by pleural cavities. These pleural cavities help lubricate the lungs with a substance called surfactant, and provide surface tension to keep the lung against the rib cage.

Lungs also have a generous capacity, meaning that in the event of a disease of one, the other may overcompensate and take on its role as well. It is for this reason that persons with lung disease may not recognize symptoms until it is very late, when lung capacity has decreased significantly. The lung environment is usually moist, which makes it an easy target for microbial infection.

Functions of the Lungs
The primary function of the lungs is respiration; to ensure waste gas (carbon dioxide) is filtered from the blood and re-oxygenate red blood cells.
Along with this main function, however, there are many other functions that the lungs serve, including:

  • Changing blood pH by altering carbon dioxide partial pressure
  • Acting as a filter for small blood clot
  • Filtering out tiny gas bubbles created during decompression following diving
  • Helps regulate body temperature ( by panting)
  • Allows for wide variety of vocal sounds by changing airflow patterns
  • Acting as shock absorbent layer for the heart which it envelopes
  • Ensures air inhaled is sterile via production of mucus with antimicrobial compounds
  • May affect the action of some systemic drugs and enzymes
  • Converts angiotensin 1 to angiotensin 2 via angiotensin converting enzyme

Problems That May Affect the Lungs
Collectively, lung disease is the third leading cause of death, but a diagnosis is often delayed until the condition has progressed significantly. Diseases may affect any part of the lungs, from the trachea all the way down to the alveoli.
These diseases, according to area may include:

  • The Windpipe (Trachea)
    • Asthma- this is the most common disease of the trachea.
    • Allergies- caused by pollen or an infection
    • Bronchitis
    • Emphysema
    • Cystic Fibrosis
    • Chronic Obstructive Pulmonary Disease
  • The Alveoli
    • Pneumonia- caused by an infection
    • Tuberculosis- a type of slow progressive pneumonia
    • Lung Cancer- this is the main area that cancers of the lung originate
    • Pneumoconiosis- a category of conditions caused by inhalation of an irritant such as asbestos
    • Emphysema
    • Pulmonary Edema- accumulation of fluid in the lungs
  • The Interstitium
    • The interstitium is the thin lining between alveoli.
    • Interstitial Lung Disease
    • Pneumonia
    • Pulmonary Edema

Miscellaneous Diseases affecting the Lungs
Diseases may also affect the blood vessels called the pulmonary arteries, the pleura or the muscles associated with breathing.