1 88 



APPLIED ANATOMY. 



Superior Mediastinum. The upper level of the superior mediastinum is 

 oblique, as it runs from the upper edge of the sternum to the first thoracic vertebra. 

 The lower level of the superior mediastinum runs from the junction of the first and 

 second pieces of the sternum to the upper border of the fifth (or lower border of the 

 fourth) thoracic vertebra. Laterally it is bounded by the pleurae and apices of the lungs. 



The distance from the anterior surface of the spine to the posterior surface of the 

 sternum is quite small, being only 5 to 6 cm. (2 to 2%^ in.). Through this pass 

 most important structures. The trachea and oesophagus are in the median line as well as 

 the remains of the thy tmis gland. To each side are the great vessels, the innominate 

 artery being on the right and the subclavian and carotid on the left. The left innomi- 

 nate vein crosses transversely just below the top of the sternum to meet the innominate 

 vein of the right side and form the superior vena cava. Into the innominate veins 

 empty the inferior thyroid, vertebral, superior intercostal, internal mammary, and 



CEsophagu 



Innominate arte 

 Left innominate ve 

 Arch of aorta 



Sternum 

 Ascending aorta 



Right ventricle 

 Right auricle. 



Diaphragm 



Trachea 



V thoracic vertebra 



Right pulmonary 

 artery 



-eft auricle 



.(Esophagus 



iferior vena cava 



Spigelian lobe 



FIG. 208. The superior (red), anterior (blue), middle (yellow), and posterior (green), mediastina. 



(Modified from Piersol.) 



pericardial veins ; and into the descending vena cava empties the vena azygos major. 

 On the posterior surface of the oesophagus and afterwards to its left side passes the 

 thoracic duct. The trachea bifurcates opposite the junction of the first and second 

 pieces of the sternum, and the transverse portion of the arch of the aorta rises as high 

 as the middle of the manubrium. The phrenic nerves lie against the pleura, the 

 right having the vena cava to its inner side. 



The right vagiis {pneumogastric} nerve comes down between the innominate 

 artery and vein and passes downward on the posterior surface of the oesophagus. It 

 gives its recurrent laryngeal branch off at about the right sternoclavicular joint. 

 The left vagus nerve comes down to the outer side of the left carotid artery and 

 goes over the arch of the aorta, giving off its recurrent laryngeal branch, and thence 

 proceeds to the anterior surface of the oesophagus. The presence of the trachea in 



