1230 



THE RESPIRATORY SYSTEM 



The apex (figs. 994, 997, 998) is rounded and points upward with an inclination 

 forward and medially, accommodating itself to the structures within and about 

 the superior aperture of the thorax. 



A deep interlobar fissure [incisura interlobaris] (figs. 994, 998), reaching 

 through the lung substance nearly to the hilus, divides each organ into a smaller 

 superior lobe [lobus superior] and a larger inferior lobe [lobus inferior]. The 

 interlobar fissure runs downward and forward beginning a short distance below the 

 apex, and reaching the base near the anterior margin in the left lung, somewhat 

 further back in the right lung. From the obliquity of the plane of the fissure it 

 will be noticed that the inferior lobe reaches posteriorly to within a short distance 

 of the apex, and includes the greater part of the back and base of the lung, while 

 the superior lobe takes in the anterior margin and apex. The presence of a mid- 

 dle lobe [lobus medius] disturbs the symmetry of the right lung. This results 

 from a deep, nearly horizontal incisure cutting through the lung somewhat below 

 its middle, and extending between the anterior margin and the main interlobar 

 fissure, which it reaches at about the level of the axillary line. 



Fig. 



994. — Left Lung, viewed from the Mediastinal Surface. 



Subclavian groove 

 I 



(Spalteholz.) 



Costal surface — ' 



Interlobar fissure 



Left branch of pulmo- _. 

 nary artery 



Left bronchus — 



Pulmonary lymph- 

 glands 



Groove for thoracic __ 

 aorta 



Pulmonary ligament — 



Inferior lobe. 



Inferior margin 



Hilus, with line of section 

 of the pleura 



'"""" Mediastinal surface 



-^^Left pulmonary veins 

 — ^-Cardiac fossa 



—Anterior margin 

 ^ '0~*Superior lobe 

 — Lingula 



Interlobar fissure 



I 



Diaphragmatic surface 



Besides possessing the individual peculiarities mentioned, the two lungs further differ from 

 each other in general form and weight, the right lung being considerably broader and heavier 

 than the left. The difference in length maintained by some anatomists, even if it prove constant, 

 must be slight and of little practical importance. These differences seem to follow the asym- 

 metry of the vault of the diaphragm and the position of the heart. 



The hilus (fig. 994), already mentioned as situated on the mediastinal surface, presents in 

 the left lung a raquette-shapcd outline. It.s average height is about 8.8 cm. (Luschka);it 

 extends over both lobes. The hilu of (lie right lung, rather four-sided in outhne and shorter 

 than that of the left, is related to the three lobes. The entering structures, constituting the 

 root of the lung (figs. 989, 99.'i, 994), incrlude the bronchus, pulmonary artery and veins, bron- 

 chial vessels, lymphatic vessels and glands, and pulmonary nerves. These are bound together 

 by connective tissue and invested by the pleura. The bronchus is in the posterior and upper 

 part of the root; the pulmonary vessels lie anteriorly, the veins below the arteries. 



The surface of the lung is marked ofT in polygonal areas of different sizes (secondary lobules) 

 by lines containing pigment. The pigmentation is especially deep on the lateral surface along 

 the furrows corre.sponding to the ribs. 



