PARATHYRIOD GLANDS -

1. They develop from the endoderm of the embryo.
2. The parathyroid glands consist of four separate glands located on the posterior surface of the lobes of the thyroid gland.
3. The cells of parathyroid glands are arranged in a compact mass and are of two types: small chief cells or principal cells and large oxyphil cells (or eosinophil cells).
4. The cells are enclosed by a delicate connective tissue capsule. The chief cells are much more numerous than the oxyphil cells. The latter are absent in the young and appear a little before the age of puberty.