Overview of the Endocrine System
Calcium is a mineral, vital to the formation of bone and teeth, blood clotting, and proper functioning of the brain nerves and muscles. The four parathyroid glands embedded in the thyroid gland function in the homeostasis of calcium, secreting parathyroid hormone (PTH), which raises blood levels of calcium, an effect opposite to that produced by the thyroid hormone, calcitonin. (PTH and calcitonin balance each other’s effects and minimize fluctuations in blood calcium concentration.) Specifically, parathyroid hormone causes mineralized bone to decompose and release calcium into the blood. Specialized cells, called osteoclasts, actually break down the bone. Parathyroid hormone also stimulates the uptake of calcium through the renal tubules.
Keywords: calcium | gland | homeostasis | hormone | human | osteoclast | parathyroid | endocrine system
- Campbell, N.A., and Reece, J.B. (2002). Biology, 6th Edition. San Francisco, CA: Pearson Benjamin Cummings.
- Clark, Joe O.E. (1999). A Visual Guide to the Human Body. London: Barnes and Noble, Inc.
- What You Need To Know About: Thyroid Cancer. Illustration courtesy of the National Cancer Institute, NIH.
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