264 



AORTA. 



to the left, and descends on the left side of the vertebral column to 

 the fourth lumbar vertebra. Hence it is divided into ascending 

 arch and descending aorta. 



Relations. The ascending aorta has in relation -with it, in front, 

 the trunk of the pulmonary artery, thoracic fascia, and pericardium ; 

 behind, the right pulmonary veins and artery ; to the right side, the 

 right auricle and superior cava ; and to the left, the left auricle and 

 the trunk of the pulmonary artery. 



Fig. 102 * 



* The large vessels which proceed from the root of the heart, with their relations ; 

 the heart has been removed. 1. The ascending aorta. 2. The arch. 3. The thoracic 

 portion of the descending aorta. 4. The arteria innominata dividing into, 5, the right 

 carotid, which again divides at 6, into the external and internal carotid; and 7, the 

 right subclavian artery. 8. The 'axillary artery : its extent is designated by a dotted 

 line. 9. The brachial artery. 10. The right pneumogaslric nerve running by the side 

 of the common carotid, in front of the right subclavian artery, and behind the root of 

 the right lung. 11. The left common carotid, having to its outer side the left pneumo- 

 gastric nerve, which crosses the arch of the aorta, and as it reaches its lower border is 

 seen to give off the left recurrent nerve. 12. The left subclavian artery becoming 

 axillary, and brachial in its course, like the artery of the opposite side. 13. The trunk 

 of the pulmonary artery connected to the concavity of the arch of the aorta by a fibrous 

 cord, the remains of the ductus arteriosus. 14. The left pulmonary artery. 15. The 

 right pulmonary artery.' 16. The. trachea. 17. The right bronchus. 18. The left 

 bronchus. 19, 19. The pulmonary veins. 17, 15, and 19, on the right side, and 14, 

 18, and 19, on the left, constitute the roots of the corresponding lungs, and the relative 

 position of these vessels is carefully preserved. 20. Bronchial arteries. 21,21. Inter- 

 costal arteries ; the branches from the front of the aorta above and below the number 3 

 are pericardiac and oesophageal branches. 



