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Brachiocephalic trunk: why it is only on the right, and how it divides

Where is the brachiocephalic trunk?

Three branches leave the aortic arch for the head and arms. If there are two sides, why three? Because on the right, the vessels to the head and arm leave as a single trunk: the brachiocephalic trunk.

teamLabBody with the brachiocephalic trunk (yellow) selected, rising to the right from the aortic arch and dividing into the right subclavian and right common carotid arteries
Screen from teamLabBody Pro, an anatomy app ›

In the view above it is yellow, running a short distance up and to the right from the aortic arch before dividing into the right subclavian artery, heading sideways, and the right common carotid artery, heading up. It lies just behind the manubrium of the sternum, rises obliquely in front of the trachea, and divides behind the right sternoclavicular joint. It is only a few centimetres long, and its length and level of division vary.

Why only on the right

The aorta arches back and to the left after leaving the heart. From the top of the arch, from right to left, arise the brachiocephalic trunk, left common carotid and left subclavian arteries. On the right, the subclavian and common carotid share one trunk; on the left they arise directly, because the leftward-curving arch lies within reach. The brachiocephalic veins, by contrast, exist on both sides, an easy point to confuse. Branching patterns vary, with frequencies that differ between studies and textbooks.

Name and terms

Brachio- means arm and cephalic means of the head. In English it is usually called a trunk rather than an artery, though brachiocephalic artery is also used. The Latin is truncus brachiocephalicus.

See it in the app

Short and hidden behind the sternum, the brachiocephalic trunk is easy to overlook among the arch branches. In the 3D anatomy app teamLabBody you can make the bones translucent, keep only the arch and its branches, and see the trunk rise to the right and divide; compared with the left branches, the right-only trunk is obvious at a glance. Cross sections are available with the PREMIUM plan.

FAQ

Where is the brachiocephalic trunk?
Behind the upper sternum, rising to the right from the aortic arch and dividing behind the right sternoclavicular joint into the right subclavian and right common carotid arteries.
Is there a brachiocephalic trunk on the left?
No. On the left the common carotid and subclavian arteries arise separately from the arch. There are, however, left and right brachiocephalic veins.
What are the three branches of the aortic arch?
From right to left: the brachiocephalic trunk, left common carotid artery and left subclavian artery.

Related articles

・Aorta: the arch it arises from

・Subclavian artery: its branch to the right arm

・Common carotid artery: its branch to the head

・Superior and inferior venae cavae: the brachiocephalic veins form the superior vena cava

・Sternum: lies in front of it

・Anatomy by body system

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