Adrenal Gland Cross-Section
Labels and Functions
| Region | Position | Hormone(s) | Function |
|---|---|---|---|
| Zona Glomerulosa | Outermost cortex | Aldosterone (mineralocorticoid) | Na+ reabsorption in DCT; K+ secretion; increases blood volume and BP |
| Zona Fasciculata | Middle cortex (widest zone) | Cortisol (glucocorticoid) | Gluconeogenesis, anti-inflammatory, stress response, immunosuppression |
| Zona Reticularis | Inner cortex | Androgens — DHEA, androstenedione | Secondary sexual characteristics (minor androgenic contribution) |
| Adrenal Medulla | Core (innermost) | Adrenaline (80%), noradrenaline (20%) | Fight-or-flight: ↑HR, ↑BP, ↑blood glucose, bronchodilation |
Key Regulatory Inputs
- Zona Glomerulosa: Angiotensin II (RAAS) + high serum K+ + ACTH → Aldosterone
- Zona Fasciculata: ACTH (from anterior pituitary, driven by CRH from hypothalamus) → Cortisol
- Zona Reticularis: ACTH → Androgens
- Adrenal Medulla: Preganglionic sympathetic nerve fibres → Adrenaline + Noradrenaline release
Embryological Origin
- Cortex: Mesoderm (intermediate mesoderm)
- Medulla: Neural crest cells (neuroectoderm) — functionally a modified sympathetic ganglion