Adrenal Medulla Flashcards

Explore the adrenal medulla, its chromaffin cells, sympathetic innervation, catecholamine secretion, vascular supply, and development.

Card 1 of 28Question

What is the adrenal medulla?

The inner, catecholamine-secreting region of the adrenal gland.

In This Section

1. What is the adrenal medulla?

The inner, catecholamine-secreting region of the adrenal gland.

2. Which part of the adrenal gland surrounds the medulla?

The adrenal cortex, with its innermost zona reticularis adjacent to the medulla.

3. What is the principal endocrine cell type of the adrenal medulla?

Chromaffin cells.

4. What are chromaffin cells developmentally equivalent to?

Modified postganglionic sympathetic neurons.

5. How are chromaffin cells typically arranged within the adrenal medulla?

In irregular clusters and cords surrounding sinusoidal blood vessels.

6. Why are adrenal medullary endocrine cells called chromaffin cells?

Their catecholamine-containing granules produce a brown coloration when treated with chromium salts.

7. Which two catecholamines are primarily secreted by the adrenal medulla?

Epinephrine and norepinephrine.

8. Which catecholamine usually accounts for most adrenal medullary secretion?

Epinephrine.

9. What is the embryological origin of adrenal medullary chromaffin cells?

Neural crest cells that migrate into the developing adrenal gland.

10. Which division of the autonomic nervous system directly controls adrenal medullary secretion?

The sympathetic nervous system.

11. What type of sympathetic nerve fibers directly innervate adrenal chromaffin cells?

Preganglionic sympathetic fibers.

12. Which nerves carry most preganglionic sympathetic fibers to the adrenal medulla?

The thoracic splanchnic nerves, particularly the greater splanchnic nerve.

13. Which neurotransmitter is released onto adrenal chromaffin cells by preganglionic sympathetic fibers?

Acetylcholine.

14. Which receptors on chromaffin cells respond to acetylcholine?

Neuronal nicotinic acetylcholine receptors.

15. How do chromaffin cells differ from typical postganglionic sympathetic neurons?

They release catecholamines into the bloodstream rather than primarily at neuroeffector junctions.

16. What is the primary precursor for catecholamine synthesis in the adrenal medulla?

The amino acid tyrosine.

17. Which enzyme catalyzes the rate-limiting step of catecholamine synthesis?

Tyrosine hydroxylase, which converts tyrosine to L-DOPA.

18. Which enzyme converts norepinephrine into epinephrine?

Phenylethanolamine N-methyltransferase (PNMT).

19. Which adrenal cortical hormone promotes epinephrine synthesis in the medulla?

Cortisol, which promotes expression of phenylethanolamine N-methyltransferase.

20. What are catecholamines stored in before secretion from chromaffin cells?

Membrane-bound dense-core secretory granules.

21. What cellular mechanism releases catecholamines from chromaffin cells?

Calcium-dependent exocytosis of secretory granules.

22. What is the principal physiological role of adrenal medullary catecholamines?

To support the sympathetic fight-or-flight response during acute stress.

23. Which two vascular pathways provide blood to the adrenal medulla?

Cortical sinusoids and direct medullary arterioles.

24. Where does blood from the adrenal medullary sinusoids ultimately drain?

Into the central medullary vein, which drains toward the suprarenal vein.

25. What distinctive smooth muscle arrangement is found in the central adrenal medullary vein?

Prominent longitudinally oriented smooth muscle bundles in its wall.

26. Which endocrine tumor arises from adrenal medullary chromaffin cells?

Pheochromocytoma.

27. What is the characteristic functional abnormality of many pheochromocytomas?

Excessive catecholamine production, often causing episodic or sustained hypertension.

28. What are extra-adrenal tumors of sympathetic or parasympathetic paraganglionic tissue called?

Paragangliomas.