Parathyroid Glands Flashcards

Study the parathyroid glands, including their location, embryological development, microscopic structure, blood supply, and calcium regulation.

Card 1 of 30Question

What are the parathyroid glands?

Small endocrine glands that secrete parathyroid hormone to regulate calcium and phosphate metabolism.

In This Section

1. What are the parathyroid glands?

Small endocrine glands that secrete parathyroid hormone to regulate calcium and phosphate metabolism.

2. How many parathyroid glands are typically present?

Four, consisting of two superior and two inferior parathyroid glands.

3. Where are the parathyroid glands usually located?

On or near the posterior surfaces of the lateral lobes of the thyroid gland.

4. What is the typical shape and color of a normal parathyroid gland?

A small, oval or flattened, yellowish-brown structure.

5. What is the approximate size of a normal adult parathyroid gland?

Approximately 5 to 6 mm long, 3 to 4 mm wide, and 1 to 2 mm thick.

6. Where are the superior parathyroid glands most commonly located?

Near the middle of the posterior thyroid lobes, often close to the cricothyroid junction.

7. Where are the inferior parathyroid glands most commonly located?

Near the inferior poles of the thyroid lobes, although their positions are more variable.

8. Which embryonic pharyngeal pouch gives rise to the superior parathyroid glands?

The dorsal portions of the fourth pharyngeal pouches.

9. Which embryonic pharyngeal pouch gives rise to the inferior parathyroid glands?

The dorsal portions of the third pharyngeal pouches.

10. Why are the inferior parathyroid glands more variable in location?

They migrate farther during development alongside the thymus, allowing greater positional variation.

11. Where may ectopic inferior parathyroid glands be found?

Within the thymus, thyrothymic ligament, or anterior mediastinum.

12. Where may ectopic superior parathyroid glands occur?

In retropharyngeal or retroesophageal locations, or occasionally within the thyroid gland.

13. What connective tissue structure surrounds each parathyroid gland?

A thin fibrous capsule that sends delicate connective tissue septa into the gland.

14. What are the two principal endocrine cell types in the parathyroid glands?

Chief cells and oxyphil cells.

15. Which parathyroid cells produce and secrete parathyroid hormone?

Chief cells, also called principal cells.

16. What is the typical microscopic appearance of parathyroid chief cells?

Small polygonal cells with round nuclei and relatively pale or lightly eosinophilic cytoplasm.

17. What are the characteristic histological features of oxyphil cells?

Larger cells with abundant eosinophilic, mitochondria-rich cytoplasm.

18. How does adipose tissue within the parathyroid glands change with age?

Stromal adipose tissue generally increases from childhood into adulthood.

19. Which artery provides the principal blood supply to most parathyroid glands?

The inferior thyroid artery, usually arising from the thyrocervical trunk.

20. Which additional artery may contribute to the blood supply of the superior parathyroid glands?

The superior thyroid artery, a branch of the external carotid artery.

21. How does venous blood drain from the parathyroid glands?

Primarily through the thyroid venous plexus into the superior, middle, and inferior thyroid veins.

22. Where does lymph from the parathyroid glands primarily drain?

To the deep cervical and paratracheal lymph nodes.

23. What autonomic nerve fibers reach the parathyroid glands?

Predominantly sympathetic vasomotor fibers from the cervical sympathetic ganglia.

24. Which membrane receptor allows parathyroid chief cells to detect extracellular calcium?

The calcium-sensing receptor (CaSR).

25. What happens to parathyroid hormone secretion when blood ionized calcium decreases?

Parathyroid hormone secretion increases.

26. What is the overall effect of parathyroid hormone on blood calcium concentration?

It increases blood calcium by acting on bone and kidneys and indirectly increasing intestinal calcium absorption.

27. How does parathyroid hormone affect renal phosphate handling?

It decreases phosphate reabsorption in the proximal renal tubules, increasing urinary phosphate excretion.

28. What is the anatomical relationship between the parathyroid glands and the recurrent laryngeal nerve?

The recurrent laryngeal nerve courses near the posterior thyroid gland and is an important landmark during parathyroid surgery.

29. Why must parathyroid blood supply be preserved during thyroidectomy?

Devascularization can impair parathyroid hormone secretion and cause postoperative hypocalcemia.

30. What is the most common pathological cause of primary hyperparathyroidism?

A benign parathyroid adenoma, usually involving a single gland.