PhysiologyLesson 5 of 11 in the course The Endocrine System

Parathyroid Hormone and Calcium Homeostasis

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

The parathyroid glands help maintain blood calcium within a range that supports healthy bones, muscle activity, and nervous system function. This lesson explores where the glands are located, how parathyroid hormone (PTH) raises blood calcium, and what can happen when calcium regulation is disrupted.

The parathyroid glands are small, round structures usually embedded in the posterior surface of the thyroid gland. A thick connective tissue capsule separates each gland from the thyroid tissue. Most people have four parathyroid glands, although additional glands may occasionally occur in tissues of the neck or chest.

All flashcards

Where are the parathyroid glands usually located?
They are usually small, round structures on the posterior surface of the thyroid, separated from thyroid tissue by a connective tissue capsule.
What are the roles of chief cells and oxyphil cells in the parathyroid glands?
Chief cells produce and secrete PTH. The function of oxyphil cells is not clearly understood.
How does PTH affect bone?
PTH promotes osteoclast-mediated bone breakdown, releasing calcium, and inhibits osteoblasts, reducing bone deposition.
How does PTH promote intestinal calcium absorption?
PTH stimulates the kidneys to produce calcitriol, the active form of vitamin D, which increases intestinal absorption of dietary calcium.
How does calcitonin affect blood calcium?
Released by thyroid parafollicular cells when blood calcium is high, calcitonin inhibits osteoclast activity, reduces intestinal calcium absorption, and decreases kidney calcium reabsorption.

Quiz questions

  1. How many parathyroid glands do most people have?Answer: Four glands
  2. Besides calcium, which mineral's reabsorption in the kidneys is increased by PTH?Answer: Magnesium
  3. Which combination describes calcitonin's effects on calcium balance?Answer: It reduces osteoclast activity and calcium absorption and reabsorption.
  4. What can excessive PTH activity do to blood calcium and bone density?Answer: Raise blood calcium and reduce bone density.
  5. Why can hypoparathyroidism cause muscle twitching and spasms?Answer: Low blood calcium increases cell membrane permeability to sodium.

Based on Anatomy and Physiology 2e by J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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