Which of the following is the characteristic histological feature that distinguishes the zona fasciculata of the adrenal cortex from the zona reticularis?

Explanation

## Adrenal Cortex Zonal Architecture ### Zona Fasciculata Histology **Key Point:** The zona fasciculata is characterized by **lipid-rich cells (spongiocytes) arranged in radial columns** perpendicular to the capsule, with abundant smooth endoplasmic reticulum (SER) for steroid synthesis. ### Zona Reticularis Histology **Key Point:** The zona reticularis consists of **deeply staining, irregular anastomosing cords** with fewer lipid droplets and more compact nuclei, reflecting its role in androgen production. ### Comparative Table | Feature | Zona Fasciculata | Zona Reticularis | | --- | --- | --- | | **Arrangement** | Regular radial columns | Irregular anastomosing cords | | **Lipid content** | Abundant (spongiocytes) | Sparse | | **Staining** | Pale/vacuolated | Dark/compact | | **SER abundance** | Abundant | Moderate | | **Primary product** | Cortisol, corticosterone | Androgens (DHEA, androstenedione) | ### High-Yield Mnemonic **Key Point:** **FAR** = **F**asciculata = **A**bundant lipid in **R**adial columns; **R**eticularis = **R**eticular (irregular) cords with **R**educed lipid. ### Clinical Pearl The abundant SER in zona fasciculata reflects high 17α-hydroxylase and 11β-hydroxylase activity for cortisol synthesis, whereas zona reticularis has higher 17,20-lyase activity for androgen production.