278 



AORTA, 



the branches of that trunk with their subdivisions, which together consti- 

 tute the efferent portion' of the systemic circulation ; and then the pul- 

 monary artery as the efferent trunk of the pulmonary circulation. 



Fig. 145.* 



AORTA. 



The AORTA arises from the left ventricle, at the middle of the root of the 

 heart, and opposite the articulation of the fourth costal cartilage with the 

 sternum. At its commencement it presents three dilatations, called the 

 sinus aortici, which correspond with the three semilunar valves. It as- 

 cends at first to the right, then curves backwards and to the left, and de- 

 scends on the left side of the vertebral column to the fourth lumbar verte- 

 bra. Hence it is divided into ascending arch and descending aorta. 



* 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 pneumogastric nerve running by the side 

 of the common carotid, in front of the right subclavran 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 axil- 

 lary 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 posi- 

 tion of these vessels is preserved. 20. Bronchial arteries. 21, 21. Intercostal arteries; 

 the branches from the front of the aorta above and below the number 3 are pericardiao 

 and oesophageul branches. 



