Zona Fasciculata Flashcards

Study the zona fasciculata, its cellular arrangement, histological features, cortisol synthesis, vascular supply, and regulation.

Card 1 of 27Question

What is the zona fasciculata?

The middle and thickest layer of the adrenal cortex, specialized for glucocorticoid production.

In This Section

1. What is the zona fasciculata?

The middle and thickest layer of the adrenal cortex, specialized for glucocorticoid production.

2. Between which two adrenal cortical zones is the zona fasciculata located?

Between the outer zona glomerulosa and inner zona reticularis.

3. Approximately what proportion of the adult adrenal cortex is occupied by the zona fasciculata?

Approximately 75% of the cortical thickness.

4. How are endocrine cells arranged in the zona fasciculata?

In long, straight, radially oriented cords, commonly one or two cells thick.

5. What type of blood vessels separate the cellular cords of the zona fasciculata?

Fenestrated sinusoidal capillaries.

6. What are the characteristic steroid-producing cells of the zona fasciculata called?

Spongiocytes.

7. Why do zona fasciculata cells appear pale and vacuolated in routine histological sections?

Their abundant lipid droplets are dissolved during tissue processing.

8. What is the principal substance stored in the lipid droplets of zona fasciculata cells?

Cholesterol esters used as precursors for steroid hormone synthesis.

9. Which two organelles are especially abundant in zona fasciculata cells?

Smooth endoplasmic reticulum and mitochondria.

10. What type of mitochondrial cristae are characteristic of zona fasciculata cells?

Tubular or tubulovesicular cristae.

11. Which class of steroid hormones is primarily synthesized by the zona fasciculata?

Glucocorticoids.

12. What is the principal glucocorticoid secreted by the human zona fasciculata?

Cortisol.

13. Which anterior pituitary hormone primarily regulates zona fasciculata activity?

Adrenocorticotropic hormone (ACTH).

14. Which hypothalamic hormone stimulates ACTH secretion?

Corticotropin-releasing hormone (CRH).

15. Which intracellular signaling pathway is activated by ACTH in zona fasciculata cells?

The cyclic adenosine monophosphate (cAMP) and protein kinase A pathway.

16. Which protein transports cholesterol into the inner mitochondrial membrane during steroidogenesis?

Steroidogenic acute regulatory protein (StAR).

17. Which enzyme converts cholesterol into pregnenolone in zona fasciculata cells?

Cholesterol side-chain cleavage enzyme (CYP11A1).

18. Which enzyme catalyzes the final step of cortisol synthesis?

11-beta-hydroxylase (CYP11B1), which converts 11-deoxycortisol into cortisol.

19. How does cortisol regulate ACTH secretion?

Through negative feedback on the hypothalamus and anterior pituitary.

20. At what time of day does cortisol secretion normally reach its highest levels in a typical daytime-active adult?

In the early morning, around the time of awakening.

21. What is a major metabolic effect of cortisol?

It increases hepatic gluconeogenesis and helps maintain blood glucose during stress.

22. How does cortisol affect inflammatory and immune responses?

It suppresses inflammatory signaling and reduces many immune responses.

23. In which direction does blood flow through the sinusoids of the zona fasciculata?

From the outer adrenal cortex inward toward the zona reticularis and medulla.

24. How does cortisol from the zona fasciculata influence adrenal medullary function?

It promotes epinephrine synthesis by increasing phenylethanolamine N-methyltransferase expression.

25. What happens to the zona fasciculata during prolonged ACTH deficiency?

It undergoes atrophy, reducing cortisol-producing capacity.

26. What happens to the zona fasciculata during sustained excessive ACTH stimulation?

It may undergo hyperplasia and hypertrophy, increasing cortisol secretion.

27. Which clinical syndrome results from prolonged excessive cortisol exposure?

Cushing syndrome.