Labels:text | screenshot | black | black and white | font | document OCR: ent, the By the seventh week of foetal developr loping Fig. 15.3). thyroid is located at the level of the det trachea as the pharynx grows anteriorly hected by a The gland now has two lateral lobes co p at this narrow isthmus. Thyroid follicles deve re and give stage. Cells of the ultimobranchial body incorporated into the developing thyro Then rise to the parafollicular or C-cells whic produce calcitonin.