Introduction:
The parathyroid glands are tiny, round structures usually found embedded in the posterior surface of the thyroid gland.
A thick connective tissue separates them from thyroid tissue.
Most people have 4 parathyroid glands, but some may have many,
Location:
They were found embedded in the posterior surface of the thyroid gland.
In cases of variation they may be present in the neck, chest i.e. in “Thymus” also.
Structure:
Parathyroid glands contain two types of cells,
Chief cells: Secrete “Parathyroid Hormone (PTH)”.
Oxyphil cells: Function is unknown yet.
Parathyroid Hormone:
It is a peptide hormone released in response to low calcium blood levels.
It acts in the following ways to correct the lowered blood levels of calcium.
It activates “Osteoclasts” and mobilises calcium in blood by eroding the bones.
It inhibits the “Osteoblasts” and hence prevents calcium deposition in bones.
It increases reabsorption of Calcium and Magnesium from kidney tubules.
Increases intestinal absorption of calcium.
Its secretion is inhibited by increased blood calcium levels : Negative feedback mechanism.
Disorders of Parathyroid Gland:
Hyperparathyroidism:
Hyperactivity of the parathyroid gland results in high calcium blood levels, causing severe bone deformities and spontaneous fractures.
Impairment of body functions.
Reduced responsiveness of the nervous system.
Hypoparathyroidism:
Decreased activity of the parathyroid glands results in muscle spasm, convulsions, muscle paralysis.
Commonly Asked Questions.
Write a short note on Parathyroid Glands.
Which hormones play an important role in maintaining the calcium levels in the body? Explain their mechanisms of action.