第1咽囊 咽鼓管 “是第2明 甲状舌管 開扁桃体窝 甲状服 第3咽囊 下甲状旁腺原基 廣腺原基 M 第4咽囊 颈窦 第5咽囊 foramen caecum thyroglossal cyst and fistula: a cystic remnant of the thyroglossal duct, may be found at any point along the migratory path followed by the thyroid gland; sometimes a thyroglossal cyst is connected to the outside by a fistulous canal, called thyroglossal fistula---foramen caecum: ---thyroglossal cyst and fistula: a cystic remnant of the thyroglossal duct, may be found at any point along the migratory path followed by the thyroid gland; sometimes a thyroglossal cyst is connected to the outside by a fistulous canal, called thyroglossal fistula