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Organ of the Month: The Lungs

Updated on March 17, 2015

The Lungs

The lungs are vital organs, this means that our human bodies depend on them to keep us alive. This is because they are the primary organ of the respiratory system. Their main function is gas exchange. This is done through the process of breathing. When we inhale, fresh oxygen rich air flows into our lungs, and when we exhale toxic carbon dioxide leaves the body. The right lung is divided into three lobes and the left lung is divided into two. Because the heart takes up so much room on the left side, the left lung is considerably smaller than the right.


The Supporting Structures

In order to understand what the lungs are and how they work, you need to know a little bit of about the supporting structures of the respiratory system. When we inhale through the nose or mouth, air is pull down the trachea (also known as the windpipe). The trachea branches into the primary bronchi which looks like an upside down "Y". the bronchi enter the lung tissue at the hilum, along with large blood vessels. Inside of the lungs, the bronchi branch into bronchioles, where the air travels through alveolar ducts, and empties into alveolar sacs. Oxygen and Carbon dioxide are exchanged here at the capillary level.

The Thoracic Cavity

The lungs and their supportive structures are safely nestled within the thoracic cavity. The lungs are divided by the mediastinum within the space of the thoracic cavity. Each lung is enclosed within their own pleural cavity, and protected by a double membrane called the pleural sac. The parietal pleura, which is the outer membrane of the pleural sac, lines the thoracic cavity and the mediastinum, while the visceral layer is formed around the lung. A small amount of plueral fluid exists between the space of those membranes. The pleural sac is extremely important because it maintains negative pressure in relation to the environment. Which will be described more thoroughly in the section "How Breathing Works".

The Diaphragm

Breathing is partially controlled and regulated by the level of carbon dioxide, C02, in the blood stream, because C02 raises the acidity of the blood. this fires off a red flag to the brain to send out nerve impulses that force the body to take a breath.

How Breathing Works

The diaphragm is a muscle that sits below the thoracic cavity, dividing the respiratory system from the digestive system. It plays a very important role in the mechanisms of breathing. During inhalation the diaphragm contracts, and the space between the pleural membranes decreases. This allows air to be pulled into the lungs. When the diaphragm relaxes it flattens, and the air passively exhales out of the body. When the diaphragm is at rest, there is negative pressure in the thoracic cavity. When the diaphragm contracts, the air inhaled is positive pressure which is why the thoracic cavity expands upon inhale. It can be a tricky idea to conceptualize which is why I provided the video link to demonstrate the process.

Sometimes breathing is a voluntary action, like when a yogi practices diaphragmatic breathing. For the rest of the time, our breath is controlled by a series of reflex actions dictated by the respiratory center of the brain.

Organ Donation

Organ donation of lung tissue is for patients who suffer from restrictive lung disease, emphysema, pulmonary hypertension, or other noninfectious end stage pulmonary disease. Whether or not a patient needs a partial, single, or double lung transplant is determined by the disease process. A living person may donate the lower lobes of their lungs for a patient in need.The procurement of lung tissue is extremely precise and time sensitive, because lung tissue has a limited period of viability.

For more information please go to, where you can learn about what it means to be an organ donor.

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My Favorite, Inexpensive, Anatomy Reference Book!

"The lungs are a pair of large cone-shaped, spongy organs that remove waste carbon dioxide from the body and exchange it for a fresh supply of oxygen. Air is drawn into the lungs by expanding the chest cavity and then expelled by allowing the cavity to collapse or by forcing the air out."


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    • toknowinfo profile image

      toknowinfo 2 years ago

      Thanks for sharing your knowledge. We often take for granted our amazing body. In September I got pneumonia. I am better now, but it was painful to take a breath, and it took a long time to recuperate. Your hub is very informative, easy to read, and well written. Voted up, useful, interesting and awesome!