The arch of the aorta or aortic arch (Latin: arcus aortae) is the portion of the aorta between its ascending and descending parts. It lies within the mediastinum.
The aortic arch begins when the ascending aorta emerges from the pericardium. It passes upward, backward, and to the left, travels through the superior mediastinum, and ends on the left side at the level of 4th/5th thoracic vertebrae. The arch extends as high as the midlevel of the manubrium of the sternum. It is initially in front of and, finally, lateral to the trachea.
Three branches arise from the superior side of the arch. In the order in which they branch off from the arch (from right to left), they are: brachiocephalic trunk, left common carotid artery, and left subclavian artery. All three are crossed anteriorly by the left brachiocephalic vein.
The brachiocephalic trunk is the largest branch, it arises behind the manubrium of the sternum, and divides further into the right subclavian artery and the right common carotid artery. The right subclavian artery passes laterally, superior to the clavicle, and then runs underneath the clavicle, passing into the upper limb. The right common carotid artery travels upwards on the right side of the neck, posteromedial to the internal jugular vein. It supplies arterial blood to the right side of the head and neck.
The left common carotid artery, unlike the right one, arises directly from the arch of the aorta. It originates to the left of the brachiocephalic trunk, ascends along the left side of the neck, and provides blood supply to the left side of the head and neck.
The left subclavian artery originates from the aortic arch to the left from the left common carotid artery. It ascends next to the left common carotid artery, both travel through the superior mediastinum on the left side of the trachea. The subclavian arteries mainly supply the arms, while some branches supply the thorax and head.