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Overview of the lungs

The lungs are part of the respiratory (breathing) system and are located in the chest, inside the rib cage and above the diaphragm. Lungs are complex organs that consist of spongy, elastic tissue that is designed to take in oxygen and get rid of carbon dioxide.


Oxygen enters the lungs when we inhale a breath. It is distributed throughout the lungs by a system called the bronchial tree, which has branches of decreasing diameter (called bronchi and bronchioles). The bronchial tree carries oxygen to small sacs (alveoli) deep within the lung where oxygen (taken from the air that is inhaled) moves from the lung into the blood stream, and carbon dioxide (a by-product of our metabolism) moves from the blood into the lung to be exhaled. Taking in oxygen, and delivering that oxygen (via the blood) to the tissues is necessary for all of the cells in our body to function. The removal of carbon dioxide is necessary to maintain the blood’s pH at an appropriate level as part of the body’s system of acid-base balance.


Since the air we breathe contains many components from the environment (such as dust, pollens, bacteria, viruses, smoke and volatile chemicals), the lungs maintain a system of defence against these potentially toxic invaders. The lungs’ defence system relies on immune cells and the secretion of mucus, both of which contain and remove these unwanted components from the lungs.


Last Review Date: November 6, 2017