8 4 THORAX 



soon as they have pierced the fibrous pericardium, are in rela- 

 tion with the serous layer merely along the medial and lateral 

 borders of the orifices in the fibrous layer through which 

 they enter. 



Dissection. After the examination of the reflections of the 

 serous layer of the pericardium is completed, the dissectors 

 should study the vessels and nerves which supply the walls of 

 the heart. They are the coronary arteries and the cardiac veins 

 and nerves, and they lie in the coronary and longitudinal sulci 

 of the heart, which have been noted already. To display them 

 the visceral pericardium superficial to them must be cut and 

 turned aside ; the fat which lies in the sulci around the vessels 

 must be removed ; then the main vessels can be traced to their 

 origins and terminations, and an endeavour should be made to 

 preserve the fine nerves which accompany the vessels. 



Arteriae Coronarise. The coronary arteries are the nutrient 

 vessels of the heart. They spring from dilatations of the com- 

 mencement of the aorta which are called the sinus aorta 

 (Valsalva). There are three sinuses of the aorta, an anterior 

 and two posterior, and only two coronary arteries, a right and 

 a left ; the right artery springs from the anterior sinus, and 

 the left from the left posterior sinus (Figs. 20, 38). 



The right coronary artery passes forwards from the anterior 

 aortic sinus, between the pulmonary artery and the auricle of 

 the right atrium ; turns downwards and to the right, in the 

 coronary sulcus, to the lower part of the right margin of the 

 heart, round which it curves. Then it proceeds to the left, in 

 the posterior part of the coronary sulcus, till it reaches the 

 posterior end of the inferior longitudinal sulcus, where it 

 divides into a small transverse and a large interventricular 

 branch. The transverse branch continues to the left, in the 

 coronary sulcus, till it anastomoses with the circumflex branch 

 of the left coronary artery. The interventricular branch runs 

 forwards in the inferior longitudinal sulcus on the diaphrag- 

 matic surface of the heart, and it anastomoses with the 

 interventricular or descending branch of the left coronary 

 artery at the cardiac notch on the lower margin of the heart. 

 In addition to its terminal brancheSj the right coronary artery 

 supplies branches to the roots of the pulmonary artery and 

 the aorta, and to the walls of the right atrium and the right 

 ventricle, the larger and more numerous branches being given 

 to the ventricle. One of the latter, the marginal branch, 

 passes along the inferior margin of the heart towards the 

 apex of the ventricle (see Fig. 39). 



