Aorta : Branches of the aorta

Three great vessels arise from the top of the aortic arch. On the right is the innominate artery, which divides into the right subclavian artery and the right common carotid artery for the head and neck. On the left there is no innominate, the left subclavian and carotid arising directly from the arch. Only the lower parts of these vessels lie within the thorax, the level of the innominate bifurcation being at the inner end of the clavicle; they are closely applied to the trachea. The corresponding veins lie more superficially and there is an innominate vein on both sides; the vessel equivalent to the common carotid is the internal jugular vein. The small coronary arteries spring from the very beginning of the aorta, immediately above the semilunar valves. There is a right and left vessel, and any disease of these impairs the circulation in the muscular wall of the heart.

The descending aorta gives off on each side the pairs of intercostal arteries that encircle the chest in the intercostal spaces; the corresponding veins do not enter the venae cavae directly but through intervening channels, the azygous veins.

The aortic arch forms a great sweep from the front of the chest to the back, with an upward convexity from which arise the main arteries of the head, neck, and arms. The concavity of the arch embraces the pulmonary arteries and veins and the bronchi, entering the roots of the lungs. There is also a little artery running the length of the back of the sternum, from above downwards. This is the internal mammary artery, a branch of the subclavian in the neck; it ends below by entering the sheath of the rectus muscle as the superior epigastric artery to anastomose (see anastomosis) with the inferior epigastric from below.