Brachiocephalic trunk (anatomy)

The brachiocephalic trunk is the first branch of the arch of the aorta to emerge as the latter passes superiorly, posteriorly and slightly to the left from the heart. It is formed deep to the centre of the manubrium sterni and it projects superiorly and obliquely to the right. In its inferior, proximal portion its relations include:

• anterior: left brachiocephalic vein
• posterior: anterior, right surface of trachea and fibres of the right vagus nerve
• posterior and left: left common carotid artery
• right: right brachiocephalic vein

At the level of the right sternoclavicular joint, it divides into the right subclavian artery and right common carotid trunk. At this point its relations are similar to those described above except:

• it comes to lie on the right lateral side of the trachea
• anteriorly and superior to the jugular notch are the sternohyoid and sternothyroid muscles
• the inferior thyroid veins are sited on its left
• the vagus nerve is more lateral

The brachiocephalic trunk supplies arterial blood to the right arm and the right side of the head and neck. Rarely, it gives off one branch - the thyroidea ima artery.

Infrequently, the left common carotid artery may originate from the brachiocephalic trunk instead of the aorta. Rarely, the right common carotid artery originates directly from the arch of the aorta and the right subclavian originates distal to the left subclavian from the left side. The anomalous right subclavian artery passes posterior to the trachea and oesophagus and can constrict them - a vascular ring.