IN HUMAN HEART

the atrial branches of the right coronary artery are sometimes described as anterior, lateral (right or marginal) and posterior groups, they are usually small single vessels 1mm in diameter. The right anterior and lateral branches are occasionally double, very rarely triple, and mainly supply the right atrium. The posterior branch is usually single and supplies the right and left atria. The artery of the sinoatrial node is an atrial branch, distributed largely to the myocardium of both atria, mainly the right. Its origin is variable: it comes from the circumflex branch of the left coronary in 35%. However, more commonly it arises from the anterior atrial branch of the right coronary artery, less often from its right lateral part, least often from its posterior atrioventricular part. This ‘nodal' artery thus usually passes back in the groove between the right auricular appendage and aorta. Whatever its origin, it usually branches around the base of the superior vena cava, typically as an arterial loop from which small branches supply the right atrium. A large ‘ramus cristae terminalis' traverses the sinu-atrial node .it would seem more appropriate to name this branch the ‘nodal artery', as most of the currently named vessel actually supplies the atria and serves as the ‘main atrial branch'

nodal artery usually identified by its course -- described above

REFER : GRAY'S ANATOMY 40 th edition vascular supply and lymphatic drainage of heart (Fig. 56.18A–C);