Anatomy, Histology, and Ultrastructure, Parathyroid, Mouse

Abstract

As in the rat and hamster, the parathyroid glands are derived from the third pharyngeal pouch. The fourth pharyngeal pouch does not develop, and therefore only one pair of glands is found. Because of the close embryologic relationship between thymus and parathyroids ectopic parathyroid tissue can sometimes occur in the thymus or close to the larynx and ectopic thymic tissue can occasionally be observed close to the parathyroid (Fig.357). In aged OF1 mice ectopic parathyroid tissue which is embedded within the thyroid gland can sometimes be found (Pour et al. 1983; see p. 333 this volume). Cysts lined by cuboidal or columnar (ciliated) epithelium and filled with eosinophilic or mucinous basophilic material (Fig. 358) seen to be remnants of embryonic ducts between primordial thymus and parathyroids.