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1. either one of a pair of spongy saclike respiratory organs within the thorax of higher vertebrates, which oxygenate the blood and remove its carbon dioxide
2. any similar or analogous organ in other vertebrates or in invertebrates


Paired, air-filled respiratory sacs, usually in the anterior or anteroventral part of the trunk of most tetrapods. They lie within the coelom and are covered by peritoneum. In mammals they are within special chambers of the coelom known as pleural cavities and the peritoneum is termed pleura.

Amphibian lungs are often simple sacs, with only small ridges on the internal walls. In higher forms the lungs become more and more subdivided internally, thus increasing greatly the surface areas across which the respiratory exchange takes place. However, even in many reptiles the lungs may be quite simple. Birds have especially complex lungs with a highly differentiated system of tubes leading into and through them to the air sacs which are contained in many parts of the bird's body. Mammalian lungs are simpler, but in them the internal subdivision into tiny sacs or alveoli is extreme; there may be over 350,000,000 of them in one human lung.

In humans the two lungs lie within the chest, separated by the heart and mediastinum. The right lung has three lobes and the left lung two. A bronchus, an artery, and a vein enter each lung medially at the hilum; each branches again and again as it enters the lobules and smaller divisions of the lungs (see illustration). The terminal airways or bronchioles expand into small clusters of grapelike air cells, the alveoli. The alveolar walls consist of a single layer of epithelium and collectively present a huge surface. A small network of blood capillaries in the walls of the alveoli affords surfaces for the actual exchange of gases. See Respiration, Respiratory system

The human lungenlarge picture
The human lung


Either of the paired air-filled sacs, usually in the anterior or anteroventral part of the trunk of most tetrapods, which function as organs of respiration.
References in periodicals archive ?
Without the collaboration of civil society government and professional alone can't do what a centre like National Heart Foundation is doing.
Communications manager for the National Heart Foundation, Aimee Brock, said nurses from district health boards, primary health organisations, in public health roles and working in regional sports agencies were among those at the conference.
Goldman, Vascular Biology Research Program, Division of Heart and Vascular Diseases, National Heart, Lung, and Blood Institute (NHLBI), 6701 Rockledge Drive, Suite 10192, MSC 7956, Bethesda, MD 20892-0001 USA, 301-435-0560, fax: 301-480-2858, e-mail: goldmans@nhlbi.
Of particular note are several downloadable books, in an easy to read and culturally sensitive format, from the National Heart, Lung, and Blood Institute; they illustrate well the use of the Internet as a publishing tool and not just a means for Web surfing.
For people who are looking to monitor their blood pressure more than once or twice a year, the National Heart, Lung and Blood Institute offers the following suggestions.
No experts--at the American Heart Association; National Heart, Lung, and Blood Institute; or elsewhere--would take that risk.
OUR campaign to raise money for the National Heart Research Fund has been an outstanding success.
The truth is that the Jarvik 2000 devices, at a cost of pounds 60,000 each, were paid for by the National Heart Research Fund.
A study from National Heart, Lung, and Blood Institute's (NHLBI) Framingham Heart Study, reported in the July 1, 1999 issue of The New England Journal of Medicine, indicated that MVP is less common and less serious than previously thought.
People who learn healthy behaviors when they're young tend to keep up their regimen for several years, thus reducing their risk for cardiovascular disease later in life, reports the National Heart, Lung, and Blood Institute.
New data from the National Heart, Lung, and Blood Institute (NHLBI), part of the National Institutes of Health, shows that the number of women who die from heart disease has shifted from one in three women to one in four - a decrease of nearly 17,000 deaths from 2003 to 2004.
Muscat: In an unprecedented surgical achievement, surgeons at the Cardiac Catheter Department of the Royal Hospital's National Heart Centre performed a catheter operation under local anesthesia while working in real time collaboration with doctors in Italy through live conferencing.

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