Lungs/Definition of Lungs

All the Alveoli on one side constitute a lung. There is a pair of lungs in the thoracic cavity. The chest wall is made up of 12 pair of ribs and the rib muscles called intercostal muscles. A thick muscular structure,called diaphragm, is present below the lungs.
The left lungs is slightly smaller and has two lobes and the right lung is bigger three lobes.They are spongy and elastic organs.The lungs also have blood vessels that are the branches of the pulmonary arteries and veins.Each lung is enclosed by two membranes called the outer pleural membrane and the inner pleural membrane.The membranes enclose a fluid which provides lubrication for the free expanding and contracting of the lungs.