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lung
(lung)
either of two large organs lying within the chest cavity, one on either side of the heart; they supply the blood with oxygen inhaled from the outside air and dispose of waste carbon dioxide in the exhaled air, as a part of the process known as respiration. Other functions include filtration of blood, serving as reservoirs to store blood, and playing a role in metabolic activities.
The lungs are made of elastic tissue filled with interlacing networks of tubes and sacs carrying air, and with blood vessels
carrying blood. The bronchi, which bring air to the lungs, branch out within the lungs into many smaller tubes, the bronchioles, which culminate in clusters of tiny air sacs called alveoli, whose total runs into millions. The alveoli are surrounded by a network of capillaries. Through the thin membranes of the
capillaries, the air and blood make their exchange of oxygen and carbon dioxide. The lungs are divided into lobes, the left lung having two and the right having three. Protecting each lung is the pleura, a two-layered membrane with lubricating fluid between its layers. See illustration at respiratory system.
Copyright 2007. An Elsevier publication. All rights reserved.
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