Parathyroid glands grown from endoderm tissue, ie, the third and fourth pharyngeus sulcus. Parathyroid glands from four pharyngeus sulcus tend to unite with the upper pole of the thyroid gland, parathyroid glands that form the cranial. Glands from third pharyngeus sulcus is part of caudal parathyroid glands, which are sometimes fused with the lower pole of thyroid. However, the position is often highly variable. Caudal portion of the parathyroid glands can be found in the posterolateral lower pole of the thyroid gland, or in the thymus, even in the mediastinum. Parathyroid glands sometimes found in the thyroid gland parenchyma. (R. Sjamsuhidajat, Wim de Jong, 2004, 695)
Normally there are four parathyroid glands in humans, which is located just behind the thyroid gland, two embedded in the superior pole of the thyroid gland and two in the inferior pole. However, the location of each of the parathyroid and the numbers can be quite varied, parathyroid tissue is sometimes found in the mediastinum.
Each of the parathyroid glands are approximately 6 millimeters, 3 millimeters wide and two millimeters thick and has a blackish brown fat macroscopic picture. Parathyroid gland contains mainly the adult primary cells (chief cells) containing Golgi apparatus striking plus the endoplasmic reticulum and secretory granules that synthesize and secrete parathyroid hormone (PTH). Tues oksifil fewer but larger granules containing oksifil and a large number of mitochondria in the cytoplasm In humans, before puberty is only rarely found, and after that the number of these cells increases with age, but the majority of young animals and humans, the cell is not found oksifil . Oksifil cell function is still unclear, these cells may be modified or the rest of the main cells that no longer secrete various hormones.
Physiology of the Parathyroid Gland
Parathyroid glands secrete parathyroid hormone (PTH), which together with Vitamin D3, and calcitonin regulate calcium levels in the blood. PTH synthesis is controlled by the plasma calcium levels, which inhibited the synthesis when high calcium levels and stimulated when calcium levels are low. PTH stimulates renal tubular reabsorption of calcium, increases the absorption of calcium in the small intestine, whereas inhibiting reabsorption of phosphate and calcium release from bone. So PTH will actively work on three major target point within the control of calcium homeostasis in the kidney, bone and intestine. (R. Sjamsuhidayat, Wim de Jong, 2004, 695)