The brachiocephalic vein, also called the innominate vein, is a paired large and valveless venous blood vessel that is formed by the confluence of the internal jugular vein and subclavian vein just behind the sternoclavicular joint.

The brachiocephalic veins are found within the upper thorax. Their primary function is to drain deoxygenated blood from the systemic circulation back to the right side of the heart (right atrium) via the superior vena cava.

As mentioned before, the union of the internal jugular and subclavian veins is known as the venous angle. It is an important anatomical landmark, as it usually receives the thoracic duct on the left side and the right lymphatic duct on the right side. Therefore, it is the site where the lymph is drained into the venous circulation.

The right and left brachiocephalic veins appear slightly asymmetrical:

The right brachiocephalic vein originates behind the sternal end of the right clavicle. It is a short vein and has an almost vertical course. After it arises, it descends vertically and joins the left brachiocephalic vein at the level of the inferior aspect of the first right costal cartilage. The right brachiocephalic vein is found anterolateral to the brachiocephalic trunk and right vagus nerve (CN X). The phrenic nerve runs posterolaterally to it.
Like on the right side, the left brachiocephalic vein also originates posterior to the sternoclavicular joint. Then it takes an oblique course and passes downward and medially, descending towards the first right costal cartilage, where it joins with the right brachiocephalic vein. The left brachiocephalic vein courses from left to right behind the manubrium of the sternum, going anterior to the left subclavian artery and left common carotid artery, as well as the trachea and brachiocephalic trunk. The left phrenic nerve and left vagus nerve (CN X) are found posterolateral to it. The aortic arch is positioned below it.

The union of both brachiocephalic veins forms the superior vena cava (Read more!).

Overall, both brachiocephalic veins are short vessels. The right brachiocephalic vein is only about 0.8 - 1.2 inches (2 - 3 centimeters) long, while the left brachiocephalic vein measures approximately 2.4 - 3.2 inches (6 - 8 centimeters). This length difference happens due to the position of the superior vena cava, which is found more on the right side. Therefore, the left brachiocephalic vein is slightly longer than its right counterpart.

The main tributaries of the brachiocephalic veins include the following vessels:

Vertebral veins (Read more!)
Inferior thyroid veins (Read more!)
Internal thoracic veins (Read more!)
Supreme intercostal vein (Read more!)
Left superior intercostal vein (the right superior intercostal vein usually drains into the azygos vein; therefore, only the left brachiocephalic vein receives the superior intercostal vein)
Pericardial veins
Thymic veins

Overall, the brachiocephalic veins drain venous blood from the head, neck, upper limbs, and upper part of the thorax. Venous blood from the head is drained through the internal jugular veins, while blood from the upper limbs reaches the brachiocephalic veins via the subclavian veins.

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Brachiocephalic vein