The parathyroid glands are four in number. They lie on the thyroid gland. They produce parathormone hormone.
Origin: It originates from embryonic ectoderm.
Location: They are found embedded in the thyroid gland. Two glands are found on the dorsal surface of each lobe of the thyroid gland.
Structure: They are round in shape. They weigh 50 mg each and have a diameter of 4-6mm. Histologically, it has two types of cells.
i)Chief cells: They are smaller, cuboidal, non-granular, and more numerous cells.
ii)Oxyphil cells: They are larger, polyhedral, granular, and less numerous cells.
These cells are enclosed by a delicate connective tissue capsule. The chief cells are endocrine in function and the function of cells is unknown.
Function: It secretes parathormone(PTH)/Collip's hormone. PTH regulates calcium and phosphate metabolism in the body. When PTH is released, calcium level in the blood returns to normal as it draws calcium from the blood, increases calcium absorption from the digestive tract, and reduces loss of calcium from urine. This ensures proper growth of bones and clotting of blood.
Disorders: They are as follows.
i)Tetany: It is caused by the hyposecretion of PTH or removal of the parathormone gland. It is characterized by twitching of muscles, spasms, sustained contractions in the larynx, hands, and feet.
ii)Hyperparathyroidism: It is caused due to the hypersecretion of PTH. It draws more calcium from the blood causing decalcification, softening of bones making it easier for ones to fracture. Self-precipitation of calcium in the kidney may lead to the formation of kidney stones.