table 13.1 of Kardong is used to create the taxon-specific developmental relationships here, although some omissions are made for simplicity., In humans and chick it emerges from pouches 3 and 4, but in mice it is exclusively generated by the third pouch

Either of the two pairs of small, spherical, encapsulated glands which develop from ventral growths of the third and fourth pharyngeal pouches and are closely associated with the external jugular veins. Calcitonin and parathyroid hormone are secreted by these glands.[AAO], Any one of several small structures, usually four, attached to the dorsal surfaces of the lateral lobes of the thyroid gland. [TFD][VHOG]

uberon

parathyroid secreting cell, epithelial body

The evolution of the tetrapods, and the shift from an aquatic to a terrestrial environment, was believed to have required new controls for regulating calcium homeostasis, and thus the evolution of parathyroid glands (...) both the tetrapod parathyroid and the gills of fish contribute to the regulation of extracellular calcium levels. It is therefore reasonable to suggest that the parathyroid gland evolved as a result of the transformation of the gills into the parathyroid glands of tetrapods and the transition from an aquatic to a terrestrial environment. This interpretation would also explain the positioning of the parathyroid gland within the pharynx in the tetrapod body. Were the parathyroid gland to have emerged de novo with the evolution of the tetrapods it could, as an endocrine organ, have been placed anywhere in the body and still exert its effect.[well established][VHOG]

UBERON:0001132

Parathyroid glands are found in all adult tetrapods, although they vary in their number, and in their exact position. Mammals typically have four parathyroids, while other groups typically have six. Fish do not possess parathyroid glands, although the ultimobranchial glands, which are found close to the oesophagus, may have a similar function and could even be homologous with the tetrapod parathyroids. Even these glands are absent in the most primitive vertebrates, the jawless fish, but as these species have no bone in their skeletons, only cartilage, it may be that they have less need to regulate calcium metabolism. The conserved homology of genes and calcium-sensing receptors in fish gills with those in the parathryroid glands of birds and mammals is recognized by evolutionary developmental biology as evolution-using genes and gene networks in novel ways to generate new structures with some similar functions and novel functions[WP]

• capsule of parathyroid gland

• parathyroid epithelium
• parenchyma of parathyroid gland
• capsule of parathyroid gland