Brachiocephalic trunk

Origin and course

The brachiocephalic trunk is the first and the largest artery to arise from the aortic arch. Thus, its branching is commonly used to denominate the end of the ascending aorta and the beginning of the aortic arch. The brachiocephalic trunk arises posterior to the center of the manubrium of sternum and courses superiorly, posteriorly and to the right.

It extends for about 4-5 cm towards the root of the neck until it reaches the right sternoclavicular joint, where it terminates by dividing into the right common carotid and right subclavian arteries.

Relations

Over its entire course, the brachiocephalic trunk lies in the superior mediastinum, where it is related to various organs and neurovascular structures. Posteriorly, the brachiocephalic trunk is related to the trachea and the right pleura. As it arises from the aortic arch, the brachiocephalic trunk crosses the anterior surface of the trachea obliquely from left to right, approximately at the level of the 9th tracheal cartilage.

Anteriorly, the brachiocephalic trunk is related to the left brachiocephalic and right inferior thyroid veins, the right cardiac branches of the vagus nerve, the thymus gland, and the sternohyoid and sternothyroid muscles. Laterally to the right, the brachiocephalic trunk is related to the right brachiocephalic vein and the upper part of the superior vena cava. Laterally to the left, the brachiocephalic trunk is related to the thymus gland, the proximal segment of the left common carotid artery, the inferior thyroid veins and the trachea.

This quiz will test you on the main arteries of the upper limb.

Branches and supply

The brachiocephalic trunk bifurcates into the right common carotid artery and right subclavian artery posterior to the sternoclavicular joint. It typically has no preterminal branches, but occasionally it can give off a bronchial, thymic, or thyroidea ima artery.

The right subclavian artery ascends through the superior thoracic aperture and enters the root of the neck. It then courses laterally above the clavicle before it descends underneath the first rib and becomes the axillary artery that goes on to supply the right upper limb. Along its course through the root of the neck, the right subclavian artery also gives off several branches to supply the head and neck.

The right common carotid artery ascends along the right side of the neck within the carotid sheath of the deep cervical fascia. It continues until it reaches the level of the superior border of the thyroid cartilage and C4 vertebra, where it bifurcates into internal and external carotid arteries. The internal carotid artery goes on to supply the brain while the external carotid artery supplies the head and neck.