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Renin Angiotensin Mechanism.

Parathyroid Gland.

 

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:

  1. 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.

  1. Hypoparathyroidism:

  • Decreased activity of the parathyroid glands results in muscle spasm, convulsions, muscle paralysis.

Commonly Asked Questions.

  1. Write a short note on Parathyroid Glands.

  2. Which hormones play an important role in maintaining the calcium levels in the body? Explain their mechanisms of action.
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