Parathyroid glands. Structure, functions

Parathyroid glands , glandulae parathyroideae, or epithelial bodies, are located on the posterior surface of the thyroid gland on each side ( sometimes only one), near the large branches of the thyroid arteries, in the thickness of loose fiber lying between the fibrous capsule of the thyroid gland and its fascial vagina : Sometimes they are outside the vagina.

Parathyroid glands are small, slightly flattened, oval or elongated, less often rounded, with a smooth shiny surface. The color of the glands in children is pale pink, they are slightly transparent, with age they take a brownish-yellowish color, which makes them slightly distinguishable from closely lying lymph nodes. The consistency of parathyroid glands is somewhat denser than that of the thyroid gland.

Parathyroid glands.

There are two pairs of glands: the two upper parathyroid glands, glandulae parathyroideae superiores, and the two lower parathyroid glands, glandulae paralhyroideae inferiores.

The number of them is not constant - from 1 to 7-8. The average weight of an individual gland ranges from 0.05 to 0.09 g. The longitudinal size of the gland is 4-8 mm, the transverse is 3-4 mm, and the thickness is 1.5-3.0 mm.

The upper glands, both the right and left, most often lie on the border of the upper and middle third of the lateral lobes of the thyroid gland, within their posteromedial surface, at the level of the lower edge of the cricoid cartilage. The lower glands, usually large in size, are located in the lower part of the lateral lobes of the thyroid gland, in the area of ​​their posterolateral surface, 0.5-1 cm above the lower edge of these lobes; Sometimes they lie in the cellulose below the thyroid gland.

Both the upper and lower parathyroid glands are more often asymmetrically disposed.

Each parathyroid gland is covered on the outside with a connective tissue capsule that sends out the processes into its thickness, dividing the gland into weakly expressed segments.

Parenchyma parathyroid glands consists of epithelial cells forming strands, between which is a connective tissue, rich in blood vessels.

The parathyroid hormone - parathyroid hormone (parathyroidin) - regulates the exchange of calcium and phosphorus in the body.

Innervation: branches from nn. Laryngei superiores et inferiores (nn. Vagi), rr. Sympathici (from truncus sympathicus).

Blood supply: branches from aa. Thyroideae inferiores et superiores. Venous blood flows through vv.thyroideae superiores and inferiores, forming the venous plexus, plexus thyroideus impar, anastomosing with the vessels of the pharynx and larynx.