Fig. 113. Upper Aperture of Thorax. 



The upper part of the Sternum, the ist and 2nd Costal Cartilages and the -muscles 

 attached to these have been removed. The Clavicles and Ribs have been pushed 

 down to their full extent. The Pericardium is exposed. The Thymus and 

 Thyreoid Glands have been cut away, together with tlie Bronchial Lymphatic 

 Glands. The Inferior Thyreoid Vessels are divided and the cervical fascia 



dissected away. 



The following structures pass upwards or downwards through the superior 

 aperture of the Thorax. 



Vessels. The right Common Carotid Arterj' rising from the Innominate 

 Artery. The Left Common Carotid a direct branch of the Arch of the Aorta. 



The Subclavian Arteries at first pass upwards into the neck and then to 

 the Axilla. 



To the right of the Arch of the Aorta lies the Superior Vena Cava formed 

 by the junction of the Right and Left Innominate Veins, which pass behind the 

 Sterno-Clavicular Articulation and the Manubrium Sterni. The Innominate Veins 

 are formed by the junction of the Internal Jugular and Subclavian Veins. The 

 large veins are situated to the outer side and in front of the main arteries. 



The Lymphatic Duct (the chief lymphatic channel) after passing upwards 

 in the posterior mediastinum where it is situated between the Aorta, Large Azygos 

 Vein and Oesophagus directs its course away from the Vertebral Column obliquely 

 upwards and to the left side of the neck; here, under cover of the deep cervical 

 fascia it forms an arch and finally opens into the Left Subclavian Vein (cf. Fig. 67). 



Nerves. The Phrenic Nerve derived from the 3rd, 4th and 5th Cervical 

 Nerves (chiefly the 4th) runs obliquely across the Scalenus Anticus Muscle to the 

 outer side of the Internal Jugular Vein, then behind this vessel between the Sub- 

 clavian Vein and Artery (Figs. 67 and 70). 



The Right Phrenic Nerve runs to the outer and anterior aspect of the 

 Vena Cava Superior, between the Pericardium and Mediastinal Pleura, along the 

 right border of the Pericardium to the Diaphragm. (Coronary Ligament of I.iver. 

 Liver and Abdominal Wall.) 



The Left Phrenic Nerve takes a greater cun'e in its passage from the 

 Neck into the Thorax owing to the asymmetry of the large vessels and is situated 

 on a deeper plane than the right, owing to the rotation of the heart to the left, 

 in its course between the Pericardium and Pleura to the Diaphragm (cf. course 

 of Phrenics in Fig. 122). 



The Vagus or Tenth Cranial Nerve 'running between the Carotid Artery 

 and Internal Jugular Vein at first passes downwards and slightly backwards but 

 soon inclines forwards to the right and in front of the Right Subclavian Artery, 

 on the left side in front of the Subclavian Artery and Aortic Arch. 



Both Vagi accompany the Oesophagus in its lower part and through the 

 Oesophageal Opening into the Abdomen on to the walls of the Stomach. The 

 left Vagus merges gradually to the Anterior Aspect whereas the right Vagus 

 becomes directed to the Posterior Aspect of the Stomach; this results from the 

 developmental rotation of the Viscus to the right. 



From each Vagus is given off a Recurrent Lar}'ngeal Nerve (Motor Nerve 

 to Muscles of the Larynx); the right recurrent nerve looping around the Sub- 

 clavian Artery whereas the left recurrent ner\'e winds round the Ductus Arteriosus 

 at its connection with the Arch of thePAorta; each nerve ascends upwards by 

 the side of the Trachea (cf. Fig. 6q). 



Viscera: The Trachea bifurcates opposite the 4th or 5th Dorsal Vertebra 

 into Right and Left Bronchus under cover of the large vessels. The Oesophagus 

 is shewn in the figure to the left of the Trachea. 



