1096 



SPLANCHNOLOGY 





Borders. The inferior border (margo inferior) is thin and sharp where it sepa- 

 rates the base from the costal surface and extends into the phrenicocostal sinus; 

 medially where it divides the base from the mediastinal surface it is blunt and 

 rounded. 



The posterior border (margo posterior) is broad and rounded, and is received into 

 the deep concavity on either side of the vertebral column. It is much longer 

 than the anterior border, and projects, below, into the phrenicocostal sinus. 



The anterior border (margo anterior) is thin and sharp, and overlaps the front 

 of the pericardium. The anterior border of the right lung is almost vertical, and 

 projects into the costomediastinal sinus; that of the left presents, below, an angular 

 notch, the cardiac notch, in which the pericardium is exposed. Opposite this 

 notch the anterior margin of the left lung is situated some little distance lateral 

 to the line of reflection of the corresponding part of the pleura. 



Groove for left subdavian artery 

 Groove for left innominate vein 



Bronchus 



Posterior 

 border 



Pulmonary 

 ligament 



Pulmonary 

 artery 



Pulmonary 

 veins 



Cardiac notch 



FIG. 973. Mediastinal surface of left lung. 



Fissures and Lobes of the Lungs. The left lung is divided into two lobes, 

 an upper and a lower, by an interlobular fissure, which extends from the costal 

 to the mediastinal surface of the lung both above and below the hilus. As seen 

 on the surface, this fissure begins on the mediastinal surface of the lung at the 

 upper and posterior part of the hilus, and runs backward and upward to the pos- 

 terior border, which it crosses at a point about 6 cm. below the apex. It then 

 extends downward and forward over the costal surface, and reaches the lower 

 border a little behind its anterior extremity, and its further course can be followed 

 upward and backward across the mediastinal surface as far as the lower part of 

 the hilus. The superior lobe lies above and in front of this fissure, and includes the 

 apex, the anterior border, and a considerable part of the costal surface and the 

 greater part of the mediastinal surface of the lung. The inferior lobe, the larger 



