Parathyroid histology

Seen under the microscope, the parathyroids are nodular structures, meaning they are shaped like a nodule, a rounded lump. They come from endoderm, one of the layers of the embryo, and they sit on the back of the thyroid, that is, on its posterior surface.

A fibrous capsule, a wrapping of tough tissue, separates the glandular tissue of the parathyroid from the tissue of the thyroid: they are neighbors, but they are not mixed together. Picture a rounded lump wrapped in its own cloth bag and resting against the thyroid. And the parathyroid's parenchyma, the tissue that does the gland's work, is made up mainly of two cell types with names of their own: chief cells and oxyphil cells. Looking at all of this is not just idle curiosity: histologic examination is an important technique for evaluating and diagnosing disorders of the gland, such as primary, secondary, and tertiary hyperparathyroidism and parathyroid carcinoma.