Rosen Ryan D., Bordoni Bruno
Michigan State University
Foundation Don Carlo Gnocchi IRCCS
The parathyroid glands are a group of endocrine glands located on the posterior thyroid. These glands are responsible for the secretion of parathyroid hormone (PTH), and play a role in calcium homeostasis. Typically, there are four glands divided into pairs - the superior parathyroid glands and the inferior parathyroid glands. The superior parathyroids generally are located superior to the inferior thyroid artery and posterolaterally to the recurrent laryngeal nerve, bilaterally. The inferior parathyroids are most commonly near the inferior pole of the thyroid and anteromedially to the recurrent laryngeal nerve, bilaterally. Branches of the inferior thyroid artery deliver arterial blood supply. Venous drainage is via the thyroid veins (superior, middle, inferior). The number and location of the parathyroid glands can be variable, with patients presenting with anywhere from three to eight parathyroid glands. Ectopic glands generally appear along the path of embryologic descent, within the carotid sheath, inside the thyroid gland, or within the superior mediastinum. Embryologically, the parathyroid glands derive from the endoderm of the third and fourth pharyngeal pouches. The third pharyngeal pouch gives rise to the inferior parathyroid glands, while the superior parathyroids arise from the fourth pharyngeal pouch. Due to their relatively long course of descent, the final location of the inferior glands is more variable.
甲状旁腺是位于甲状腺后方的一组内分泌腺。这些腺体负责分泌甲状旁腺激素（PTH），并在钙稳态中发挥作用。通常有四个腺体，分为两对——上甲状旁腺和下甲状旁腺。上甲状旁腺通常位于双侧甲状腺下动脉上方和喉返神经后外侧。下甲状旁腺最常见于双侧甲状腺下极附近和喉返神经前内侧。甲状腺下动脉的分支提供动脉血供。静脉回流通过甲状腺静脉（上、中、下）。甲状旁腺的数量和位置可能各不相同，患者的甲状旁腺数量从三个到八个不等。异位腺体通常出现在胚胎发育下降路径上，在颈动脉鞘内、甲状腺内或上纵隔内。从胚胎学角度来看，甲状旁腺起源于第三和第四咽囊的内胚层。第三咽囊产生下甲状旁腺，而上甲状旁腺则起源于第四咽囊。由于其下降过程相对较长，下甲状旁腺的最终位置变化更大。
