thyroid diverticulum thyroid diverticulum the thyroid pouch or thyroid diverticulum is the embryological structure of the second pharyngeal arch from which thyroid follicular cells derive. thyroid diverticulumdetailsprecursorsecond pharyngeal archgives rise tothyroid follicular cellsidentifierslatinsaccus thyreoideus; diverticulum thyreoideumtediverticulum_by_e5.4.1.2.0.0.9 e5.4.1.2.0.0.9 anatomical terminology it grows from the floor of the pharynx.