Adrenal gland - Functional anatomy

Adrenal gland - They are suprarenal - they sit on top of the kidneys.

Each is composed of 2 distinct regions:

A. Adrenal Medulla

- the inner region

- comprises 20% of the gland

- secretes epinephrine and norepinephrine

- derived from ectoderm 

B. Adrenal Cortex

- the outer region

- comprises 80% of the gland

- secretes corticosteroids 

- derived from mesoderm

Following are the parts of adrenal cortex

1. Zona Glomerulosa (outermost region) - produces mineralocorticoids (aldosterone)  
2. Zona Fasiculata (middle region) - produces glucocorticoids (cortisol) as well as estrogens and androgens.
3. Zona Reticularis (innermost region)  produce  adrenal androgens.