Innominate Artery

ANONYMA ARTERIA (truncus brachio-cephalicus), the innominate artery (brachiocephalic trunk), is the rightmost and anterior of the three large trunks emerging directly from the aortic arch at the transition from its ascending to its horizontal part. At the level of the right sternocostal joint, the innominate artery divides into two trunks: the right subclavian artery and the right common carotid artery, which is why it is also called the brachiocephalic trunk. From the sternum, the innominate artery is separated by the left innominate vein and the lower parts of the sternohyoid and sternothyroid muscles, and in children, also by the thymus gland. The cardiac branches of the right vagus nerve descend across its anterior surface. The innominate artery crosses the trachea obliquely and anteriorly; between them run cardiac branches from the recurrent branch of the vagus nerve and from the cervical nodes of the sympathetic nerve. In the thoracic cavity, the innominate artery lies extrapleurally at the border between the anterior and posterior mediastinum. This artery develops from the remnant (in the adult) of the fourth arterial segment of the ascending part of the first aortic arch. Failure of obliteration accounts for frequently observed anomalies in the number, position, and branching of the aortic trunks. These anomalies reduce to three types: a decrease in the number of aortic branches, an increase in their number, and a normal number with abnormal branching.