II. Anatomy
- Images
- Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
- Four Parathyroid Glands in neck, adjacent to the Thyroid Gland
- One gland positioned behind each of Thyroid poles
- Parathyroid Glands may be positioned in the superior mediastinum in some cases
III. Physiology
- Images
- Parathyroid Gland regulates extracellular Calcium
- Parathyroid synthesizes Parathyroid Hormone (PTH)
- Parathyroid increases PTH release when Calcium falls
- See Parathyroid Hormone for PTH physiology
- Parathyroid cells have a Calcium sensing receptor (CASR), triggered in Low Serum Calcium states
- PTH rises when Calcium falls, and increases Serum Calcium
- Stimulates Osteoclast activity to resorb bone
- Decreases renal Calcium excretion
- Stimulates intestinal Calcium absorption
- PTH falls when Calcium rises, and decreases Serum Calcium
- Negative feedback loop