lung

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Either of two spongy, saclike respiratory organs in most vertebrates, occupying the chest cavity together with the heart and functioning to remove carbon dioxide from the blood and provide it with oxygen.
2. n. A similar organ in some invertebrates, including spiders and terrestrial snails.
3. idiom. at the top of (one's) lungs As loudly as one's voice will allow.

Century Dictionary and Cyclopedia

1. n. One of the two spongy or saccular organs, occupying the thorax or upper part of the body-cavity, which communicate with the pharynx through the trachea, and are the organs of respiration in air-breathing vertebrates. The corresponding organs of those animals that breathe under water are the gills or branchiæ; in ordinary fishes the homologue of a lung is the air-bladder or sound, whose varying conditions are important in classification. (See physoclistous, physostomous, and sound.) Except in their least-developed condition, the lungs are formed by the repeated subdivision of the branches of their bronchi which finally end in saccular dilatations called infundibula. The infundibula and the air-passages immediately leading to them are beset with air-cells. These air-cells or alveoli are from , to of an inch in diameter. They are furnished with a close capillary network in which the branches from the pulmonary artery terminate, and the blood is separated from the air only by the capillary wall and the thin alveolar epithelium of the air-cells. This assemblage of minute saccular organs and air-bearing tubes is bound up by connective tissue into the comparatively compact lung. The bronchial arteries and veins provide for the nutrition of the pulmonary structures. Lymphatics abound, and there are numerous lymphatic glands. The vagus and sympathetic supply nerves. In man each lung is pyramidal in form, its base resting on the diaphragm and its apex rising about an inch above, the collar-bone. The right lung is divided into an upper, a middle, and a lower lobe; the left simply into an upper and a lower. At the inner side of each lung, a little above the middle, the bronchus and blood-vessels enter, forming the root of the lung; and except for this attachment the lung lies free in its pleural cavity, which it completely fills. The lung is elastic and always on the stretch. The blood, in passing through the lungs, gives off carbon dioxid to the air in the alveoli, and receives oxygen. This absorption and elimination seems to be a simple mechanical process, and independent of any secreting or other activity of the epithelial cells. In the lower vertebrates there may be but one lung, or one may be much larger than the other. A lung may lie in the general cavity of the body and be of great extent, as in serpents. The lungs are fixed and molded to the ribs in birds, and in this class the air-passages through the lungs expand into great serous sacs which occupy most parts of the body and extend into the hollow bones.
2. n. In entomology, one of the respiratory organs peculiar to those Arachnida whose tracheal system is modified into a number of lamellæ superimposed upon one another like the leaves of a book. They are also called pulmonary lamellæ and respiratory leaflets.
3. n. In pulmonate mollusks, a modification of the integument subserving aërial respiration: more fully called external lung. Huxley.
4. n. plural A bellows-blower; a chemist's servant.

Wiktionary

1. n. anatomy A biological organ that extracts oxygen from the air.

GNU Webster's 1913

1. n. (Anat.) An organ for aërial respiration; -- commonly in the plural.

WordNet 3.0

1. n. either of two saclike respiratory organs in the chest of vertebrates; serves to remove carbon dioxide and provide oxygen to the blood