The superior thyroid artery and its branches.
The superior thyroid artery arises from the external carotid artery just below the level of the greater cornu of the hyoid bone and ends in the thyroid gland.
At the apex of the lobe, it divides into anterior and posterior branches. The anterior branch first descends along the anterior border of the lobe and then continues along the upper border of the isthmus to anastomose with its fellows of opposite side. The posterior branch descends along the posterior border of the lobe to anastomose with the ascending branch of the inferior thyroid artery. Superior thyroid artery supplies the upper one-third of the lobe and upper half of the isthmus.