The parathyroid glands are located on the four poles of the thyroid. It secretes parathyroid hormone (PTH) which regulates calcium metabolism.
Capsule - enclosed by a thin layer of connective tissue.
Trabeculae - connective tissue extends inwards from the capsule to partially outline irregular lobes and lobules.
Chief Cells (#1 and #2) - the majority of cells in the parathyroid.
Small cells (5 to 8 µm diameter) with dark nuclei and thin rim of lightly stained cytoplasm.
They secrete parathyroid hormone (PTH).
Oxyphil Cells (#1 and #2) - larger cells (8 to 12 µm diameter) with dark nuclei and strongly eosinophilic cytoplasm because of numerous mitochondria. They appear after the first decade of life and are thought to be non-secretory cells.
Clear Cells (#1 and #2)- larger cells (8 to 12 µm diameter) with dark nuclei and a watery, clear cytoplasm.