Special Histology and Embryology: Practical Course - V. K. Napkhanyuk 2001

Endocrine System
Parathyroid Glands

The main functional role of the Parathyroid glands (glandulae parathyroideae) is the Regulation of Calcium METABOLISM. These glands secrete a protein hormone, parathyroid hormone (parathyrin), which acts on Bone tissue (the primary calcium reservoir) to promote calcium release and elevate its concentration in the Blood, thereby functioning as an antagonist to Calcitonin.

Each parathyroid gland is enclosed within a delicate Connective Tissue capsule. Its parenchyma consists of trabeculae—epithelial cords or clusters of endocrine epithelial Cells known as parathyroid cells (endocrinocyti parathyroidei). These cells are categorized into chief or basophilic parathyroid cells (endocrinocyti principales) and oxyphil or acidophilic parathyroid cells (endocrinocyti acidophilici).

Chief parathyroid cells feature a basophilic Cytoplasm with scattered clusters of free Ribosomes (Polysomes) along the periphery, indicating a high rate of Protein Synthesis. The well-developed Golgi apparatus is represented by dense cisternae and numerous vesicles, where secretory granules measuring 150-200 nm in diameter are formed. Cell/35.html">Mitochondria are abundant.

The chief parathyroid cells are further subdivided into:

— light (chief) parathyroid cells (endocrinocyti principales lucidi), whose cytoplasm contains Glycogen inclusions;

— dark (chief) parathyroid cells (endocrinocyti principales densi).

Chief parathyroid cells synthesize parathyroid hormone, whereas acidophilic cells are considered to be senescent forms.

Slide 4. Parathyroid gland (Fig. 18).

Low magnification. At this magnification, the thin connective tissue capsule of the gland and its parenchyma can be clearly observed.

High magnification. It is clearly visible that the parenchyma of the parathyroid gland is composed of cords (trabeculae) and clusters of endocrinocytes separated by delicate connective tissue septa. The chief parathyroid cells, characterized by basophilia, and the acidophilic (oxyphilic) parathyroid cells are easily distinguished. Among the chief cells, both light and dark variants can be identified.

On the diagram, label: 1) capsule; 2) epithelial trabeculae; 3) chief parathyroid cell; 4) acidophilic parathyroid cell.

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Fig. 18. Parathyroid gland. Hematoxylin and eosin staining. x 280:

1 — trabeculae; 2 — chief parathyroid cell; 3 — acidophilic parathyroid cell; 4 — connective tissue septa



Last update: 10/08/2026

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