Unusual thyroid gland vascularization

During a dissection course, an unusual vascularization of the thyroid gland was found in a 69-year-old human male cadaver. On the right side, two arteries from the thyrocervical trunk supplied the lower half of the right lobe of the thyroid gland: the inferior thyroid artery and an additional vessel with a main trunk, found to be split into an upper and lower branch at the level of the longus colli muscle. The upper branch supplied the inferior constrictor pharyngeal muscle and the esophagus, whereas the lower branch coursed, at first, onto the trachea and finally leaving, it to anastomose with the inferior thyroid artery.