The inferior thyroid veins appear two, frequently three or four, in number, and arise in the venous plexus on the thyroid gland, communicating with the middle and superior thyroid veins. While the superior and middle thyroid veins serve as direct tributaries to the internal jugular vein, the inferior thyroid veins drain directly to the brachiocephalic veins.
They form a plexus in front of the trachea, behind the Sternothyreoidei.
From this plexus, a left vein descends and joins the left brachiocephalic vein, and a right vein passes obliquely downward and to the right across the brachiocephalic artery to open into the right brachiocephalic vein, just at its junction with the superior vena cava; sometimes the right and left veins open by a common trunk in the latter situation.
These veins receive esophageal tracheal, and inferior laryngeal veins, and are provided with valves at their terminations in the brachiocephalic veins.