- The first and largest branch of the arch
- Arises opposite the centre of the manubrium sterni
- In front of the trachea
- As it ascends it inclines to the right to reach the posterior aspect of the right sternoclavicular joint.
- There if bifurcates into right subclavian and right common carotid arteries.
- Between it and the manubrium are the left brachiocephalic vein, thymic remnants and lower attachments of sternothyroid and sternohyoid.
- Upper portion is medial to the right brachiocephalic vein
- The right vagus is lateral to it then passes behind it to reach the right side oft he trachea.