PARATHYROID GLANDS

The parathyroid glands develop from the endoderm of the third and fourth pharyngeal pouches (Brachial Pouch). The thymus is also derived from the third pharyngeal pouch. 

• The inferior parathyroid glands are derived from the dorsal part of the third pharyngeal pouch, and the thymus arises from the ventral part of the third pharyngeal pouch.
• The superior parathyroid glands are derived from the fourth pharyngeal pouch and migrate together with the ultimobranchial bodies.

Parathyroid gland develops from 3rd and 4th branchial or pharyngeal pouches. Superior parathyroid develop from the 4th pharyngeal pouch and inferior parathyroid develop from the 3rd pharyngeal pouch.

Ref: Langman’s medical Embryology, 9th Edition, Page 384.

C i.e. ^4th branchial pouch

A i.e. Tc-Thallium Substraction Scan

• The parathyroid glands are ovoid bodies measuring about 6 mm long in their greatest diameter.
• They are four in number and are closely related to the posterior border of the thyroid gland, lying within its fascial capsule.
• The two superior parathyroid glands are the more constant in position and lie at the level of the middle of the posterior border of the thyroid gland.
• The two inferior parathyroid glands usually lie close to the inferior poles of the thyroid gland. They may lie within the fascial sheath, embedded in the thyroid substance, or outside the fascial sheath

Ans. Thallium technetium substraction scan