What is Adrenal Gland Anatomy?
Each adrenal gland sits atop a kidney and is really two glands in one: an outer cortex that produces steroid hormones and an inner medulla that produces catecholamines. Together they help regulate metabolism, blood pressure, and the stress response.
The adrenal cortex has three zones producing mineralocorticoids, glucocorticoids, and androgens, while the adrenal medulla contains chromaffin cells that release epinephrine and norepinephrine under sympathetic stimulation.
- •Zona glomerulosa → aldosterone (mineralocorticoid)
- •Zona fasciculata → cortisol (glucocorticoid)
- •Zona reticularis → androgens
- •Derived from mesoderm
- •Controlled by ACTH and the renin-angiotensin system
- •Chromaffin cells → epinephrine & norepinephrine
- •Derived from neural crest tissue
- •Functions as a modified sympathetic ganglion
- •Triggered directly by sympathetic nerve fibers
- •Drives the 'fight-or-flight' response
Step-by-step worked examples
Adrenal glands sit atop each kidney; combined weight is about 8–10 g. What proportion of that mass is cortex vs medulla?
Cortex makes up ~80-90% of gland mass Medulla makes up ~10-20% Cortex produces steroid hormones, medulla produces catecholamines
Zona glomerulosa produces aldosterone, which regulates sodium reabsorption. Roughly what percentage of filtered sodium does aldosterone-modulated reabsorption affect in the distal nephron?
Aldosterone acts on ~2-3% of filtered Na+ in the distal tubule and collecting duct This fine-tunes the final sodium balance Even a small percentage significantly affects blood volume and pressure over time
During acute stress, the medulla secretes epinephrine and norepinephrine in roughly a 4:1 ratio. If total catecholamine output is 100 units, how much is epinephrine?
Ratio epinephrine:norepinephrine ≈ 80:20 (4:1) 100 units × 0.8 = 80 units epinephrine 100 units × 0.2 = 20 units norepinephrine
Flashcards
Quick quiz
Q1.Which adrenal cortex zone produces cortisol?
Q2.What hormone does the adrenal medulla mainly release during stress?
Q3.Which zone regulates sodium and potassium balance?
Q4.The adrenal medulla develops from which embryonic tissue?
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Common mistakes
The adrenal cortex and medulla are functionally identical. — Correct: They are distinct: the cortex makes steroid hormones, the medulla makes catecholamines.
Aldosterone and cortisol come from the same zone. — Correct: Aldosterone comes from the zona glomerulosa; cortisol comes from the zona fasciculata.
The adrenal medulla is controlled mainly by ACTH. — Correct: The medulla is controlled by direct sympathetic nerve stimulation, not ACTH (which regulates the cortex).
The adrenal glands only affect the stress response. — Correct: They also regulate electrolyte balance, blood pressure, metabolism, and secondary sex characteristics.
FAQ
What is adrenal gland anatomy?
Each adrenal gland has an outer cortex (three hormone-producing zones) and an inner medulla (catecholamine-producing chromaffin cells).
What is the adrenal gland formula for hormone zones?
Use 'GFR': Glomerulosa→aldosterone, Fasciculata→cortisol, Reticularis→androgens, from outside in.
What are examples of adrenal cortex vs medulla hormones?
Cortex: aldosterone, cortisol, DHEA. Medulla: epinephrine, norepinephrine.
How is adrenal gland structure regulated?
Cortex activity is largely regulated by ACTH from the pituitary and the renin-angiotensin system; medulla activity is regulated directly by sympathetic nerves.