Parathyroid gland are situated very close to or embedded in the thyroid glands. They have connective tissue capsule, but when deeply embedded in the thyroid gland both may have a common capsule.
The parenchyma consists of anastomosing cords of cells between which are numerous capillaries. Two types of cells are described.
Chief cells: These are polygonal with lightly stained or clear cytoplasm. The cells may be small, with darkly stained nuclei.
Oxyphile cells: These are larger than chief cells but have smaller and darker staining nuclei. The cytoplasm contains fine granules and stains deeply with acid dyes.
The oxyphile cells are present only in man and ox, and only in adults or aged ones among them. The secretion parathyroid glands (parathormone) play an important role in regulation of calcium metabolism.
