THE ASCENDING AORTA 



581 



Branches. The only branches of the ascending aorta are the coronary arteries 

 which supply the heart. They are two in number, right and left, arising near the 

 commencement of the aorta immediately ahove the attached margin of the semi- 

 lunar valves. 



The Coronary Arteries (Fig. 432). The right coronary artery (a. coronoria 

 [cordis] dextra), about the size of a crow's quill, arises from the anterior sinus of 

 Valsalva. It passes forward between the pulmonary artery and the right auricular 

 appendix, then runs obliquely to the right side, in the groove between the right 

 auricle and ventricle, and, curving around the right border of the heart, runs to the 

 left along its postero-inferior surface as far as the postero-inferior interventricular 

 groove, where it divides into two branches, one of which, the transverse, continues 

 onward in the groove between the 



left auricle and ventricle, and VAGUS NERVE 



anastomoses with the left coro- 

 nary; the other, the descending 

 (ramus descendens posterior a. 

 coro nar iae [cordis] dextrae), courses 

 along the postero-inferior inter- 

 ventricular furrow, supplying 

 branches to both ventricles and 

 to the septum, and anastomosing 

 at the apex of the heart with the 

 descending branches of the left 

 coronary. 



This vessel sends a large 

 branch, the marginal, along the 

 thin margin of the right ventricle, 

 to the apex, which in its course 

 gives off numerous small branches 

 to the anterior and posterior sur- 

 faces of the right ventricle. It 

 also gives off a branch, the infundibular, which ramifies over the front part of the 

 conns arteriosus of the right ventricle. A small branch of the right coronary is said 

 to supply the auriculoventricular bundle of His (see p. 568). 



The left coronary artery (a. coronaria [cordis] sinistra], larger than the former, 

 arises from the left posterior sinus of Valsalva; it passes forward between the pul- 

 monary artery and the left auricular appendix, and divides into two branches. 

 Of these, one, the transverse, passes transversely outward in the left auriculo- 

 ventricular groove, and winds around the left border of the heart to its postero- 

 inferior surface, where it anastomoses with the transverse branch of the right 

 coronary; the other, the descending (ramus descendens anterior a. coronariae [cordis] 

 sinistrae), passes along the antero-superior interventricular groove to the apex of 

 the heart, where it anastomoses with the descending branches of the right coronary. 

 The left coronary supplies the left auricle and its appendix, gives branches to 

 both .ventricles, and numerous twigs to the pulmonary artery and commencement 

 of the aorta. 



Peculiarities. These vessels occasionally arise by a common trunk, or their number may 

 be increased to three, the additional branch being of small size. More rarely there are two 

 additional branches. 



Applied Anatomy. The sudden blocking of a coronary artery by an embolus, or its more 

 gradual obstruction by arterial disease or thrombosis, are common causes of sudden death in 

 persons past middle age. If the obstruction to the passage of blood is incomplete, true Angina 

 pectoris may occur. In this condition the patient is suddenly seized with a spasm of agonizing 

 pain in the precordial region and down the left arm, together with an indescribable sense of 

 anguish. He may die in such an attack, or succumb a few hours or days later from heart failure, 

 or he may survive a number of attacks. 



RIGHT AURICLE 



FIG. 434. Horizontal section through the sixth thoracic 

 vertebra upper surface of the lower segments-showing the 

 ascending portion of the aortic arch, the thoracic aorta, and 

 related structures. 



