Topographic Anatomy and Location
The anatomical position of the parathyroid glands (glandulae parathyroideae) is closely related to the thyroid gland. Typically, they are attached to the posterior surface of its lateral lobes. The classic anatomical norm features two symmetrical pairs:
- Superior parathyroid glands (glandulae parathyroideae superiores). Their typical location is at the junction of the upper and middle thirds of the posteromedial surface of the lateral thyroid lobes. The lower border of the cricoid cartilage serves as a topographic landmark for locating them.
- Inferior parathyroid glands (glandulae parathyroideae inferiores). Traditionally found in the lower part of the lateral thyroid lobes. Most commonly, they lie against the posterolateral surface, positioned approximately 0.5–1 cm above the lower pole of the lobes.
Crucial anatomical variability must be noted: the inferior glands are not always rigidly fixed to the thyroid gland. Sometimes they may shift and reside in the surrounding loose adipose tissue significantly lower than the main organ. Furthermore, the total number of glands is exceptionally variable. Clinical practice encounters cases of a single gland, as well as multiple variants reaching seven or even eight endocrine bodies in a single individual.
Macroscopic Structure and Physical Parameters
During visual inspection of a specimen or during surgery, the shape of the glands is described as oval, occasionally slightly flattened. Palpation reveals a firmer consistency compared to the soft tissue of the thyroid gland itself.
The color of the organ is extremely important for identification. In children, the parenchyma has a delicate pale pink hue. However, with age, the color changes: the tissue acquires a brownish-yellow shade. This age-related metamorphosis makes the parathyroid glands visually difficult to distinguish from nearby regional lymph nodes, requiring special care from surgeons and anatomists.
The physical parameters of an average single gland are small:
- Length: 4 to 8 mm.
- Width: 3 to 4 mm.
- Thickness: ranges from 1.5 to 3 mm.
- Average mass: only 0.05–0.09 g.
Microscopic Anatomy and Functions
From a histological perspective, each glandula parathyroidea is segregated from surrounding tissues. Externally, it is securely covered by its own connective tissue capsule. Delicate connective tissue septa (trabeculae) extend inward from this outer sheath, providing a structural framework.
The parenchyma of the gland is formed by clusters of specialized epithelial cells. These cells are organized into characteristic structures — forming cords and dense groups. The space between the epithelial cords is filled with stroma, consisting of loose connective tissue. This connective tissue foundation is highly vascularized, meaning it is exceptionally rich in blood vessels, which is a typical feature of an actively secreting endocrine gland.
The sole yet critically important function of the parathyroid glands is endocrine. They synthesize and release parathyroid hormone (parathormon or parathyrinum) into the bloodstream. The biological role of this hormone is the strict regulation of calcium and phosphorus metabolism in the human body, maintaining their constant levels in the blood and tissues.