The paired lungs are organs comprised of bronchi, bronchioles, alveoli, connective tissue, blood vessels, lymphatics, and nerves (see Figure 10.9). The right and left lungs are situated on either side of the medi-astinum (the part of the thoracic cavity that lies be-tween the lungs). The lung is somewhat conical, with the apex projecting just above the first rib. The base of the lung is related to the superior surface of the di-aphragm, which separates the thorax from the ab-domen. The lungs take the same contour as the inner wall of the thorax, and the lung surface in contact with the thoracic wall is known as the costal sur-face. Medially, the mediastinal surface of the lung isin contact with the structures of the mediastinum.
The lungs are separated into lobes by deep fissures. The right lung has three lobes (the superior, middle, and inferior); the left lung has only two lobes (the su-perior and inferior). A deep, oblique fissure sepa-rates the superior and the inferior lobe. In the right, ahorizontal fissure separates the superior and themiddle lobes. The right lung appears larger than the left lung; in the left, a lot of space is taken by the heart and great blood vessels. The right lung is shorter, how-ever, because the diaphragm is higher in the right as a result of the presence of the liver inferiorly.