THORACIC AND PULMONARY ANATOMY
The gross anatomic features of both the lungs are shown in figure 1. On the right side the major division between the right lower (inferior) lobe (3) and the two others is a major fissure (2) which parallels the course of the fourth rib. The height to which the superior segment extends posteriorly behind the right upper (superior) lobe (1) should be noted, since the presence of the right lower lobe at this high level is important in interpreting x-rays. Of similar importance is the position of the right middle lobe (4), whose upper margin is demarcated by the approximately horizontal fissure (5). Accordingly, the middle lobe is entirely in the anterior half of the chest. In the left lung, the superior segment of the left lower (inferior) lobe (9) extends to a similarly high posterior level beneath the left oblique fissure (7) separating the left upper (superior) (6) and lower (inferior) lobes (9). The lingula (8) is, however, incorporated with the upper lobe and occupies a relatively narrow, wedge-shaped area along the anteroinferior border of that lobe.
After removal of the entire right lung, the thoracic cavity and mediastinum might appear as in figure 2. Superiorly, the mediastinum contains the superior vena cava (1A) with the phrenic nerve (2) and the vagus nerve (3), which enters between the superior cava and innominate artery (4) and then crosses the trachea (5) to proceed along the lateral border of the esophagus (6). After received intercostal tributaries, the azygos vein (7) ascends lateral to the esophagus and then loops about the hilus of the right lung to join the superior vena cava near its junction with the right atrium. The investing visceral pleura about the hilus of the lung is shown as a cut edge as it joins the mediastinum and pericardium. Inferiorly this pleura forms the interior pulmonary ligament (8), which contains an occasional lymph node. This enclosed space of the hilum contains the right mainstem bronchus (9) in its posterosuperior position. Directly anterior to this is the right pulmonary artery (10), and then inferiorly are the right superior (11) and right inferior pulmonary veins (12), as well as a few hilar nodes. Other important nodes are those about the azygos vein (7) and the right phrenic nerve (2) on the superior vena cava. On the posterolateral chest wall are shown the intercostal neurovascular bundies (13) proceeding in their sheltered locations in grooves along the inferior border of each rib. The thoracic sympathetic nerve chain (14) is shown with its ganglia and with the origins of both the greater (15) and lesser splanchnic nerves (16).
The left thoracic cavity with the lung removed appears as in figure 3. Arising from the arch of the aorta (17) are the innominate (4), the left common carotid (18), and left subclavian arteries (19)...