7.9 Embryology, Anatomy, and Physiology of the Parathyroid Glands
10.1055/b-0038-162784
7.9 Embryology, Anatomy, and Physiology of the Parathyroid Glands
There are four parathyroid glands (in two pairs), usually close to the upper and lower poles of the thyroid lobe.
Embryology
The upper pair of parathyroid glands arises from the fourth branchial cleft and descends with the thyroid gland, usually at the cricothyroid junction. The lower pair arises from the third branchial cleft and descends with the thymus; the location of the lower parathyroids may be variable (Fig. 7.4). Ectopic parathyroids may be found anywhere along the pathway of descent of the branchial pouches. The (lower) parathyroid glands have been described in the carotid sheath, anterior mediastinum, and intrathyroid.
Fig. 7.4 Embryologic origin and descent of the parathyroid glands. (Used with permission from Terris DJ, Gourin CG, eds. Thyroid and Parathyroid Diseases: Medical and Surgical Management. New York, NY: Thieme; 2009:216.)
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