Parathyroid gland

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The parathyroid glands are four small circular glandular structures embedded in the posterior surface of the thyroid gland. They are an endocrine gland, producing parathyroid hormone (parathormone, PTH) which acts to control the level of calcium and phosphorus in the blood.

Structurally, each parathyroid gland is encased by a thin connective tissue capsule that separates it from the thyroid. Septa extend from the capsule into the gland to divide it into irregular lobules and to separate the densely packed cords of cells.

Principal cells and oxyphil cells form the epithelium of the parathyroid gland.

• Principal (chief) cells are small polygonal cells and constitute the majority of the parenchymal cells of the parathyroid. They help regulate the synthesis, storage, and secretion of large amounts of parathyroid hormone.
• Oxyphil cells are more rounded and larger than principal cells and comprise only a minor portion of the parenchymal cells. They do not fulfil any secretory role. They can occur singly or in clusters.

Watch the following video to learn more about the histological appearance of the parathyroid gland:

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