These are small glands that are directly responsible for in the endocrine system.  Located
next to the thyroid gland.  Typically there are 4 total glands but it has been
seen where some people have 6 or 8 total glands.

The parathyroid glands are somewhat superimposed onto the thyroid but the cells are largely
different from the thyroid and are easily recognizable.

The function of the parathyroid is in regards to calcium levels
Calcium is largely important in the muscular and Nervous systems to allow for muscular
movement as well as nerve conduction.

PTH   -   Parathyroid hormone  -  is produced in the parathyroid gland

PTH effects bone to either breakdown small areas of bone to release calcium or it can tell
the intestines and kidneys to increase absorption of calcium.