Anatomy. An organ for aerial respiration; commonly in the plural. "My lungs began to crow like chanticleer." (Shak) In all air-breathing vertebrates the lungs are developed from the ventral wall of the oesophagus as a pouch which divides into two sacs. In amphibians and many reptiles the lungs retain very nearly this primitive saclike character, but in the higher forms the connection with the oesophagus becomes elongated into the windpipe and the inner walls of the sacs become more and more divided, until, in the mammals, the air spaces become minutely divided into tubes ending in small air cells, in the walls of which the blood circulates in a fine network of capillaries. In mammals the lungs are more or less divided into lobes, and each lung occupies a separate cavity in the thorax. See Respiration. Medicine. Lung fever, pneumonia. Botany. Lung flower, one of the breathing organs of spiders and snails. Origin: OE. Lunge, AS. Lunge, pl. Lungen; akin to D. Long, G. Lunge, Icel. & Sw. Lunga, Dan. Lunge, all prob. From the root of E. Light. See Light not heavy. Source: Websters Dictionary. Lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart. Their principal function is to transport oxygen from the atmosphere into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere. A large surface area is needed for this exchange of gases which is accomplished by the mosaic of specialized cells that form millions of tiny, exceptionally thin-walled air sacs called alveoli. To understand the anatomy of the lungs, the passage of air through the nose and mouth to the alveoli must be studied. The progression of air through either the mouth or the nose, travels through the nasopharynx, oropharynx, larynx, and the trachea (windpipe). The air passes down the trachea, which divides into two main bronchi; these branch to the left and right lungs where they progressively subdivide into a system of bronchi and bronchioles until the alveoli are reached. These many alveoli are where the gas exchange of carbon dioxide and oxygen takes place. Breathing is driven by muscular action; in early tetrapods, air was driven into the lungs by the pharyngeal muscles via buccal pumping, which is still found in amphibians. Reptiles, birds and mammals use their musculoskeletal system to support and foster breathing. Medical terms related to the lung often begin with pulmo-, such as in the (adjectival form: pulmonary) or from the Latinpulmonarius ("of the lungs"), or with pneumo- (from Greek πνεύμων "lung"). An OSH glossary used in safety and health at work which is, adopted by ILO {102}. The term definition has been obtained from the secondary source