The Parathyroid Glands

The thyroid contains four glands called the parathyroid glands. Parathyroid glands are normally the size of a grain of rice. Occasionally they can be as large as a pea and still be normal. The four parathyroid glands are located behind the thyroid. Normal parathyroid glands are the color of spicy yellow mustard. The tube running up the center of the picture is the trachea, which the thyroid wraps around. The voice box sits on top of the trachea. The carotid arteries are shown on both sides of the thyroid running from the heart up to the brain, along with the thyroid arteries and veins that help spread hormones into the bloodstream rapidly.

These glands are a vital part of the endocrine system and serve as serum calcium regulators. They measure the amount of calcium in the blood constantly, and if the calcium levels go down a little bit, the parathyroid glands recognize it and make parathyroid hormone (PTH) which goes to the bones and takes some calcium out and puts it into the blood. Calcium is the most important element in our bodies , so calcium is regulated more carefully than any other element. PTH increases calcium concentration in the blood by increasing activity of osteoclasts (absorb Ca2+ from bones), by increasing absorption of calcium in the small intestine, and by increasing calcium reabsorption in the kidneys.