a-short-review-of-histology

The Parathyroid Glands:

There are, usually, four parathyroid glands located within the fascial sheath that encloses the thyroid gland
They are usually located along the posterior border of the thyroid lobes
Each parathyroid gland is surrounded by a thin connective tissue capsule
The secretory cells, known as chief cells and producing parathyroid hormone, are arranged in cords with fenestrated capillaries
Unlike in many endocrine glands the parenchymal cells in the parathyroid gland are quite small and their cytoplasm contains few secretory granules
This is due to the short time that normally exists between production of the hormone and its delivery out of the cell
In other endocrine glands producing a protein/polypeptide hormone there is a greater store of hormone /precursor hormone held in storage eg in the thyroid gland, there is about 3 months worth of thyroglobulin held in storage in the center of a thyroid follicle in a healthy individual
Parathyroid hormone is a calcium increasing hormone and is antagonistic to calcitonin produced by the parafollicular cells of the thyroid gland
The parathyroid gland shows age related changes
With increasing age, from puberty, many of the parathyroid hormone producing cells are replaced by adipose cells and by a group of cells whose cytoplasm contains numerous mitochondria
The function of these cells is uncertain but they are known as oxyphil cells

Section of Parathyroid Gland

Note the cords of small parenchymal cells (arrows) in this section of parathyroid gland
These are chief cells that produce the parathyroid hormone
Blood vessels (arrow heads)

Parathyroid Gland - Age Changes

In this section of parathyroid gland from an elderly person note the cords of chief cells (arrowed A)
Adipose (fat) cells are also present (B)